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Develops a theoretical model describing the adsorption kinetics of the two-dimensional first-order phase transition in monolayers. Theory including a kinetic model of the phase transition in Langmuir and Gibbs monolayers; Adsorption from bulk solution; Dissociation kinetics of bulk micelles.

The monolayer characteristics of selected N-alkanoyl substituted α-amino acid are studied with the objective to demonstrate the specific effect of the chemical structure of the polar head group which is highlighted with the D- and L-enantiomers of the following selected examples: R-alanine, R-serine, R-threonine, R-allo-threonine, and R-aspartic acid (R = C 16 , C 18). The thermodynamic effect of the head group variation is studied. Experimental π-A isotherms of the N-tetradecyl-L-alanine monolayers show similar behavior as those of usual amphiphiles. The -CH 3 -group in R-alanine with the simplest head group structure is substituted by a -CH 2 -OH group in R-serine and serine methylester and by a -CH- CH 3 -OH group in R-threonine (or allo-threonine) and threonine methylester. The introduction of the methyl group in 3-position of serine (serine to 3-methyl-serine = threonine) shifts the characteristic temperatures by >20 K to lower values determined for N-C16-D l -serine. The formation of the corresponding methylester decreases these temperatures by 15 K for serine with the shorter (C16) alkyl chain and only by ∼5 K for threonine with the longer chain (C18). The π–A curves of the enantiomeric and racemic allo-forms show similar features to those of N-stearoyl-threonine. The absolute T 0 -values (disappearance of the LE/LC-transition) are 4–5 K larger compared with the corresponding N-stearoyl-threonines, but the ΔT 0 between the enantiomeric (D) and the racemic (DL) forms is only slightly larger than that of N-stearoyl-threonine. Monolayers of different N-alkanoyl substituted α-amino acid amphiphiles have been mesoscopically characterized. Substantial topological differences are observable at the condensed phase domains of several amino acid amphiphiles, such as, N-palmitoyl aspartic acid, N-palmitoyl- or N-stearoyl serine methyl ester, N-stearoyltyrosine, N-palmitoyl or N-myristoyl alanine. Many fascinating domain shapes are found, but always the curvatures of the two enantiomeric forms are directed in an opposite sense. The domain shape of the 1:1 racemic mixtures is usually different, but very often oppositely curved texture elements are observable. GIXD is used to study the characteristic features of the lattice structure of condensed monolayer phases on the Angstrom scale. Specific for all structures is the large tilt angle with respect to the surface normal, which decreases only marginally by compression. The large size of the head groups and strong interactions between them dominate the monolayer structure. As presented for N C16 and N-C18-threonine, N-C16-DL -serine, N-C16-L -serine, N C16 DL -serine-ME, N C16 L -serine-ME, N C18 DL -threonine-ME, and N C18 L -threonine-ME the enantiomers form an oblique lattice structure (3 diffraction peaks), whereas two peaks are observed for the racemates forming NNN tilted orthorhombic structures. A complete phase diagram of mixed monolayers of the D- and L-enantiomers of N-stearoyl-threonine with two eutectic points at x D ≈ 0.25 and x D ≈ 0.75 is proposed. The quantum chemical semiempirical PM3 method is applied to calculate the thermodynamic and structural parameters of clusterization in finite and infinite clusters for N-alkanoyl-substituted alanine with n = 8–17 carbon atoms in the chain at the air/water interface with the aim to obtain a new theoretical verification of the experimental results. [Display omitted] • monolayer characteristics of selected N-alkanoyl substituted α-amino acids (R-alanine, R-serine, R-threonine, R-allo-threonine, and R-aspartic acid [R = C 16 , C 18 ]) • Thermodynamic effect of the head group variation; mesoscopical characterization • GIXD studies of lattice structure of condensed monolayer phases • Phase diagram of mixed D- and L-enantiomers of N-stearoyl-threonine monolayers • Application of the semiempirical PM3 method [ABSTRACT FROM AUTHOR]

The introduction of the highly-sensitive imaging technique Brewster angle microscopy (BAM) has given rise to new knowledges about the mesoscopic topology and ordering of condensed phase domains formed in the two-phase coexistence region of Langmuir monolayers. Besides fatty acids, monoalkanoylglycerols are the most studied amphiphiles at the air−water interface. In this review, the mesoscopic characterization of amphiphilic monoglycerol monolayers is surveyed to demonstrate the striking effect of the position of the glycerol backbone at which the polar head group is substituted. Systematic mesoscopic studies of amphiphilic monoglycerol monolayers offer an outstanding possibility to highlight the dramatic effect of chemical structure variations at the position of the glycerol backbone and the substituted polar groups on the basis of the mesoscopic characterization. Small changes in the polarity by slight variation in the head group structure can dramatic affect shape and organization of the condensed phase domains. According to the importance of the 1-substituted monoglycerols, the effect of the chemical structure of the substituted polar group is highlighted with 4 selected examples. Further main topics discussed are chiral discrimination, kinetics of non-equilibrium structures, electrostatic interactions and a new geometric concept for explaining the topology of condensed phase domains. [ABSTRACT FROM AUTHOR]

The influence of the position of the aliphatic chain at the glycerol backbone has been basically unknown. Solely the results of 2-monopalmitoyl-rac-glycerol obtained at ≤13 °C indicated an essential influence of the position of the palmitoyl group at the glycerol backbone, substantiated by a disordered packing of the alkyl chains. Therefore, the present study extends the comprehensive characterization of 2-monopalmitoyl-rac-glycerol monolayers to the low-temperature range for highlighting the effect of the position of the aliphatic chain at the glycerol backbone of monoalkanoylglycerolester monolayers. Systematic studies of the thermodynamic behavior, the morphological features, and the 2D lattice structures of 2-monopalmitoyl-rac-glycerol monolayers at ≤10 °C allow useful conclusions. Large differences between the π-A isotherms of 1- and 2-monopalmitoyl-rac-glycerol monolayers and their thermodynamic analysis indicate that the change of the substitution from position 1 to position 2 of glycerol backbone is consistent with a shortening of the alkyl chain by roughly two CH2 groups. Quantum chemical calculations of the molecular structure and packing calculations are in reasonable agreement with the thermodynamic results. Considerable diversity in the mesoscopic domain topography exists between the monoalkanoylglycerol esters with the aliphatic chain positioned at the end of the glycerol backbone (1-position) and those with the aliphatic chain in the middle of the glycerol backbone (2-position). The new faceted shape of the 2-monopalmitoyl-rac-glycerol domains, before they develop branched fractal-like structures at the edges, is the essential difference to the round or cardioid-like 1-monoalkanoylglycerol domains. In the low-temperature range, well-defined orthorhombic lattice structures exist at all surface pressures. Comparing all GIXD data from the three racemic compounds (1-monostearoyl-rac-glycerol, 1-monopalmitoyl-rac-glycerol, and 2-monopalmitoyl-rac-glycerol) shows that 2-monopalmitoyl-rac-glycerol behaves as 1-monomyristoyl-rac-glycerol, i.e., the shift from position 1 to position 2 of the glycerol backbone is equivalent to a shortening of the alkyl chain. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented in which the editor discusses articles in the issue on topics including application of quantum-impurity solvers for Dynamical Mean-Field Theory (DMFT), Monte Carlo based impurity solvers and use of exact diagonalization as an impurity solver in DMFT.

The effect of chirality on the thermodynamic behavior, the morphological features, and the 2D lattice structures of 3-monopalmitoyl- sn -glycerol monolayers is studied. The results are based on measurements of the surface pressure-area ( π - A ) isotherms, Brewster angle microscopy (BAM), and Synchrotron X-ray diffraction at grazing incidence (GIXD). The π-A isotherms of the enantiomeric 3-monopalmitoyl- sn -glycerol monolayers measured between 10 and 34 °C are similar to those of the racemic 1-monopalmitoyl-rac-glycerol monolayers. Evaluating the temperature dependence of the phase transition pressure (π t ) gives access to the transition entropy. The absolute ΔS values increase as the temperature decreases demonstrating that the ordering of the condensed phase increases at lower temperatures. The comparison with the corresponding racemate shows that the condensed phase of the racemate has a higher stability indicating preferred heterochiral interactions. Similar to the racemic monoglycerol esters round and cardioid-like domains are observable but the tendency to irregular deviations in the inner texture and shape from the perfect circular domain in the mesoscopic domain topography is larger for the chiral 3-monopalmitoyl- sn -glycerol than for the racemic 1-monopalmitoyl-rac-glycerol. Systematic GIXD measurements of 3-monopalmitoyl- sn -glycerol monolayers are carried out over large pressure intervals at 5, 10, and 15 °C. The comparison of the contour plots for the three temperatures shows a shift of the contour plots displaying three separated diffraction signals, which indicate the dominance of the chiral nature, to higher lateral pressures with increasing temperature. The similarity of the lattice data obtained by fitting 3 and 2 peaks for conditions where the contour plots resemble those of NN tilted or NNN tilted orthorhombic structures demonstrates the small effect of chirality on the lattice structures in this region. The cross-sectional area, A 0 , is almost unaffected by surface pressure and temperature and amounts to values between 19.7 Å 2 and 19.8 Å 2 , as expected for a rotator phase at the lower limit. The tilt angle with respect to the surface normal t decreases with increasing pressure. The tilting transition pressure was obtained by plotting 1/cos( t ) vs. the lateral pressure and extrapolating to the zero tilt angle. The values for the untilted state are quite high and have not been reached experimentally, but they are slightly smaller than those of the corresponding racemic mixture. The lattice distortion d plotted versus sin 2 ( t ) and extrapolated to zero tilt provides the d 0 values which are slightly smaller than 0 showing that the influence of chirality on the lattice distortion is weak and decreases with increasing temperature. [ABSTRACT FROM AUTHOR]

1-Monopalmitoyl-rac-glycerol is omnipresent in numerous biological and applied systems. Systematic GIXD measurements of 1-monopalmitoyl-rac-glycerol monolayers are carried out over a large pressure interval at 5, 10, and 15 °C to construct the phase diagram on the basis of reliable 2D lattice structures. These studies are complemented by other monolayer characteristics, such as π-A isotherms and mesoscopic domain topographies. A phase transition is found between the two orthorhombic structures with NN and NNN tilted alkyl chains at low temperatures (5 and 10 °C). It increases linearly with increasing temperature. With a further increase in temperature to 15 °C, only NN-tilted orthorhombic lattices are observed in the whole pressure region. The cross-sectional area, A 0, is less affected by surface pressure and temperature and amounts to values of between 19.7 and 19.8 Ų, as expected for a rotator phase at the lower limit. The tilt angle t with respect to the surface normal decreases with increasing pressure and is only slightly influenced by the temperature. The transition pressure to untilted alkyl chains, as determined by the extrapolation of 1/cos(t) to zero tilt angle, is >50 mN/m for all temperatures. The results of lattice distortion d versus sin 2(t) suggest for 10 and 15 °C the tilt of the aliphatic chains as the reason for the monolayer lattice distortion whereas at 5 °C the nonzero-tilt-angle intercept d 0 could be an indication of the prevention of hexagonal packing. The generic π-T phase diagram of racemic monoacylglycerol monolayers is constructed on the basis of the phase diagrams of 1-monopalmitoyl-rac-glycerol and 1-monostearoyl-rac-glycerol, which shows that for 1-monopalmitoyl-rac-glycerol monolayers the oblique phase can occur only close to and below 0 °C. The possible phase behavior of other racemic monoacylglycerol monolayers with alkyl chain lengths of C14 and C20 is discussed on the basis of the generic phase diagram. [ABSTRACT FROM AUTHOR]

For understanding the role of amide containing amphiphiles in inherently complex biological processes, monolayers at the air-water interface are used as simple biomimetic model systems. The specific characteristics of the condensed phases and phase transition in insoluble and adsorbed monolayers of amide amphiphiles are surveyed to highlight the effect of the chemical structure of the amide amphiphiles on the interfacial interactions in model monolayers. The mesoscopic topography and/or two-dimensional lattice structures of selected amino acid amphiphiles, amphiphilic N-alkylaldonamide, amide amphiphiles with specific tailored headgroups, such as amide amphiphiles based on derivatized ethanolamine, e.g. acylethanolamines (NAEs) and N-,O-diacylethanolamines (DAEs) are presented. Special attention is devoted the dominance of N,O-diacylated ethanolamine in mixed amphiphilic acid amide monolayers. The evidence that a first order phase transition can occur in adsorption layers and that condensed phase domains of mesoscopic scale can be formed in adsorption layers was first obtained on the basis of the experimental characteristics of a tailored amide amphiphile. New thermodynamic and kinetic concepts for the theoretical description of the characteristics of amide amphiphile’s monolayers were developed. In particular, the equation of state for Langmuir monolayers generalized for the case that one, two or more phase transitions occur, and the new theory for phase transition in adsorbed monolayers are experimentally confirmed at first by amide amphiphile monolayers. Despite the significant progress made towards the understanding the model systems, these model studies are still limited to transfer the gained knowledge to biological systems where the fundamental physical principles are operative in the same way. The study of biomimetic systems, as described in this review, is only a first step in this direction. [ABSTRACT FROM AUTHOR]

Abstract: Knowledge of the mesoscopic morphology of condensed phase domains formed after the main phase transition in the two-phase coexistence region of Langmuir monolayers progressed rapidly with the development of the highly-sensitive imaging techniques, particularly by Brewster angle microscopy (BAM). Latest developments of commercial BAM instruments have been developed to a high technical level and allow upgrading to imaging ellipsometers which combine optical microscopy and ellipsometry and make the assessment of small layered structures or patterned thin films possible. A large variety of condensed phase domains different in mesoscopic sizes and shapes as well as their textural features has been observed which depend sensitively on the chemical structure of the amphiphilic monolayer and the system conditions, such as surface pressure and temperature. This unsuspected morphological variety of condensed phase domains has been proven not only in Langmuir monolayers but also in adsorbed monolayers (Gibbs monolayers), in Langmuir monolayers penetrated by dissolved surfactants or in adequate molecular recognition systems. The inner textures of domains can be explained on the basis of their geometry and the two-dimensional lattice in dependence of the tilt angle of the alkyl chains and gave rise to the development of a geometric concept on the basis of the molecular packing. New knowledge has been gained about non-equilibrium structures and their transition kinetics into the equilibrium state. Combined results obtained recently by BAM have enhanced the understanding of molecular organization in phase diagrams and binary mixtures. Recent advances in model studies about chiral discrimination effects and of the highly specific structural changes of host-monolayers by recognition of non-surface active guest-components have made progress. Semi-empirical quantum chemical methods have been used to gain insight into the role of different types of interactions involved in the main characteristics of mesoscopic length scale aggregates of mimetic systems. [Copyright &y& Elsevier]

The self-consistent theory of Anderson localization of quantum particles or classical waves in disordered media is reviewed. After presenting the basic concepts of the theory of Anderson localization in the case of electrons in disordered solids, the regimes of weak and strong localization are discussed. Then the scaling theory of the Anderson localization transition is reviewed. The renormalization group theory is introduced and results and consequences are presented. It is shown how scale-dependent terms in the renormalized perturbation theory of the inverse diffusion coefficient lead in a natural way to a self-consistent equation for the diffusion coefficient. The latter accounts quantitatively for the static and dynamic transport properties except for a region near the critical point. Several recent applications and extensions of the self-consistent theory, in particular for classical waves, are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Recent work has provided experimental and theoretical evidence that a first order fluid/condensed (LE/LC) phase transition can occur in adsorbed monolayers of amphiphiles and surfactants which are dissolved in aqueous solution. Similar to Langmuir monolayers, also in the case of adsorbed monolayers, the existence of a G/LE phase transition, as assumed by several authors, is a matter of question. Representative studies, at first performed with a tailored amphiphile and later with numerous other amphiphiles, also with n-dodecanol, provide insight into the main characteristics of the adsorbed monolayer during the adsorption kinetics. The general conditions necessary for the formation of a two-phase coexistence in adsorbed monolayers can be optimally studied using dynamic surface pressure measurements, Brewster angle microscopy (BAM) and synchrotron X-ray diffraction at grazing incidence (GIXD). A characteristic break point in the time dependence of the adsorption kinetics curves indicates the phase transition which is largely affected by the concentration of the amphiphile in the aqueous solution and on the temperature. Formation and growth of condensed phase domains after the phase transition point are visualised by BAM. As demonstrated by a tailored amphiphile, various types of morphological textures of the condensed phase can occur in different temperature regions. Lattice structure and tilt angle of the alkyl chains in the condensed phase of the adsorbed monolayer are determined using GIXD. The main growth directions of the condensed phase textures are correlated with the two-dimensional lattice structure. The results, obtained for the characteristics of the condensed phase after a first order main transition, are supported by experimental bridging to the Langmuir monolayers. Phase transition of adsorbing trace impurities in model surfactants can strongly affect the characteristics of the main component. Dodecanol present as minor component in aqueous sodium dodecylsulfate solution dominate largely the fundamental features of the adsorbed monolayer of the mixed dodecanol/SDS solutions at adsorption equilibrium. A theoretical concept on the basis of the quasi-chemical model and assumption of the entropy non-ideality has been developed which can well describe the experimental results of the diffusion kinetics of surfactant adsorption from solutions. The model regards the phase behaviour of adsorbed monolayers on the basis of the experimental results explicitly supported by the first order fluid/condensed phase transition and theoretical models assuming bimodal distribution between large aggregates (domains) and monomers and/or very small aggregates. Another simple theoretical model for the description of the coadsorption of surfactant mixtures, based on the additivity of the contributions brought by the solution components into the surface pressure is shown to be in qualitative agreement with the experimental data of mixed dodecanol/SDS solutions. The theoretical results corroborate the fact that the formed condensed phase (large aggregates) in the mixed monolayer consists mainly of dodecanol. [Copyright &y& Elsevier]

Abstract: Interfacial molecular recognition in artificial systems is fundamental in understanding of biological recognition processes and for potential application in material sciences. This review focuses attention on recent advances in the characterization of the highly specific structural changes of the host-monolayer by recognition of non-surface active guest-component, in understanding the interfacial recognition dynamics and in the description of recognition kinetics. [Copyright &y& Elsevier]

Abstract: The phenomenon of spontaneous non-linear oscillations, produced by surfactant transfer through a liquid membrane at the membrane/acceptor phase interface, is theoretically studied by direct numerical simulation of the model system evolution. The mathematical model, based on the first principles, includes non-linear, non-steady state Navier–Stokes, continuity and convective diffusion equations with the boundary conditions accounting for the momentum and mass balances. The oscillation mechanism and the effect of system geometry and surfactant properties on the oscillation characteristics are considered. The correlation with available experimental results is discussed as well. [Copyright &y& Elsevier]

Abstract: Spontaneous non-linear oscillations produced at the heptane/water and dodecane/water interface by dissolution of an alcohol droplet in the water bulk are studied experimentally and the results are compared with the predictions of the theory developed recently [J. Phys. Chem. B 109 (2005) 22868]. The effect of the alkane and alcohol properties on the dynamic regime and the characteristics of oscillations are analysed. Good qualitative agreement between theory and experiment is found. The effect of contaminations present in liquid phases and thermal convection due to evaporation on the behaviour of the considered systems is discussed. [Copyright &y& Elsevier]

Abstract: Over decades, information about the rheological properties of the condensed monolayer phases has been obtained by introduction of a two-dimensional compressibility which is defined on the basis of the surface pressure–molecular area (Π–A) features of the monolayer. Since the last decade, fundamental progress was attained in the experimental determination of the main characteristics of Langmuir monolayers in microscopic and molecular scale. Already smallest changes in the molecular structure of the amphiphile can result in changes in the molecular arrangement in the monolayer and thus, in changes of the main characteristics of the monolayer such as, the surface pressure–area per molecule (Π–A) isotherms, the shape and texture of the condensed phase domains and the two-dimensional lattice structure. As the classical equations of state allowed only characterisation of the fluid (gaseous, liquid-expanded) state, thermodynamically based equations of state, which consider also the aggregation of the monolayer material to the condensed phase, have been developed. The present review focuses particularly to amphiphilic monolayers, the Π–A isotherms of which indicate the existence of two condensed phases. For this case, the experimental results of the differences in the structure features and phase properties are discussed. The generalisation of the equation of state for Langmuir monolayers developed for the case that one, two or more phase transitions in the monolayer take place, is in agreement with the experimental results that the two-dimensional compressibility of the condensed phases undergoes a jump at the phase transition, whereas the compressibility is proportional to the surface pressure within one of the condensed phases. An example is presented which explains the procedure of the theoretical analysis of Π–A isotherms indicating the existence of two condensed phases. An element of the procedure is the application of the general principle that the behaviour of any thermodynamic system is determined by the stability condition. An interesting anisotropy of the compressibility is revealed by GIXD studies of the S-phase of octadecanol monolayers. However, similar studies performed close to the LS–S-phase transition would result in a thermodynamically impossible negative compressibility. Close to this phase transition, the compressibility cannot be determined from the positions of the maxima because the monolayer is in a disordered state attributed to elastic distortions by fluctuations with the structure of the new phase in the surrounding matrix without destroying the quasi-long-range positional order. [Copyright &y& Elsevier]

Abstract: Two-dimensional monolayer material of a large number of amphiphiles is transformed into overgrown three-dimensional structures in a state of metastability and supersaturation. This process is described by a theoretical concept and characterised by sensitive experimental techniques. Two theoretical models compatible with each other are based on nucleation and growth of the formed 3D nuclei: (i) the model for limiting cases of nucleation and overgrowth of 3D nuclei with assumed shapes, and (ii) the generalised model under formation of lenticular nuclei. The latter model allows determination of the nucleation rate constant which renders possible the determination of the critical nucleus size and the free energy for the formation of critical nucleus in dependence on the surface pressure. A theoretical model developed on the basis of the classical nucleation theory is applied for this. An effective double-surface pressure-step method is introduced to distinguish between the nucleation and growth processes. Consequently, a critical surface pressure, the limiting surface pressure for the formation of 3D nuclei, and an equilibrium surface pressure, at which the 3D nuclei cease to grow, can be defined and experimentally determined. Despite the different boundary conditions, the constant surface pressure relaxation data can be theoretically described by these two consistent nucleation-growth models. In the most cases, the limiting case of progressive nucleation occurs but also instantaneous nucleation is observed. Direct evidence has been provided by AFM studies that constant surface pressure relaxation of monolayers is caused by nucleation-growth of 3D nuclei from the monolayer material. The quantitative analysis of growth and distribution of the 3D micrograins by AFM supports the mechanism obtained by application of the nucleation-growth theories. New instrumental techniques such as, BAM, AFM, GIXD and X-ray reflectivity provide detailed information on the characteristics of the 3D structures overgrown on the monolayer during constant surface pressure relaxation on microscopic and molecular scales. [Copyright &y& Elsevier]

Abstract: The systems producing non-linear spontaneous oscillations of the interfacial tension and electric potential are considered and the available criteria for development of convective instability by the surfactant transfer through a liquid interface are discussed. The non-linear oscillations are observed by the surfactant transfer from a point-like source situated in the bulk of liquid, by the transfer of two ionic solutes through a liquid interface in two opposite directions, and by the transfer of ionic solutes through a liquid membrane. All these systems are governed by more complicated mechanisms than merely arising oscillatory convective instability. The main experimental results obtained for these three systems as well as theoretical models proposed for their explanation are discussed. [Copyright &y& Elsevier]

Abstract: Recent progress in studies of the main characteristics of supramolecular assemblies formed by interfacial molecular recognition between an amphiphilic monolayer and a non-surface-active species, which is dissolved in the aqueous subphase, by complementary hydrogen bonding and/or electrostatic interaction at the air–water interface is reviewed. Systems consisting of an amphiphilic melamine-type monolayer and an pyrimidine derivative dissolved in the aqueous subphase are representative model systems for molecular recognition on the basis of complementary hydrogen bonding. Most of the studies have been performed with 2,4-di(n-undecylamino)-6-amino-1,3,5-triazine (2C11H23-melamine) monolayers as host component and thymine, uracil or barbituric acid as dissolved non-surface-active pyrimidine derivatives. The combination of surface pressure studies with Brewster angle microscopy (BAM) imaging and Grazing incidence X-ray diffraction (GIXD) measurements is optimal for the characterization of the change in structure and phase behavior at the interfacial recognition process. The molecular recognition of all pyrimidine derivatives dissolved in the aqueous subphase changes drastically and in a specific way the characteristic features (π–A isotherms, morphology of the condensed phase domains) of the 2C11H23-melamine monolayer. The small condensed phase domains of the pure 2C11H23-melamine monolayer are compact without an inner texture. The monolayers of the supramolecular 2C11H23-melamine entities with thymine or uracil form specifically well-shaped condensed phase domains with an inner alkyl chain texture essentially oriented parallel to the periphery. The completely different morphology of the 2C11H23-melamine-barbituric acid monolayers is characterized by the formation of large homogeneous areas of condensed phase that transfer at smaller areas per molecule to a homogeneous condensed monolayer. The striking differences in the main characteristics between the supramolecular entities are related to their different chemical structures: complementary hydrogen bonding of two thymine or uracil molecules by one 2C11H23-melamine molecule and a linearly extended hydrogen bonding network between 2C11H23-melamine and barbituric acid. The high values of hydrogen bonding energy obtained by quantum chemical calculations on the basis of the semi-empirical PM3 method state the high stability of the supramolecular entities. The GIXD results reveal that the formation of hydrogen-bond based superstructures between the polar head groups of the amphiphilic 2C11H23-melamine monolayer and the non-surface-active pyrimidine derivatives gives rise only to quantitative changes in the two-dimensional lattice structure of the alkyl chains. The alternative possibility to construct interfacial molecular recognition systems on the basis of acid–base interaction is demonstrated by the experimental results obtained by molecular recognition of the heptadecyl-benzamidinium chloride monolayers with dissolved non-surface-active phenylacetate ions. The formation of supramolecular assemblies causes also drastical changes of the surface features in these systems. Here, the development of a substructure in the condensed phase domains consisting of long filigree strings and the favoured formation of bilayers overgrowing the strings indicates a linearly extended amidinium-carboxylate interfacial structure of the base and acid component in alternating sequence. [Copyright &y& Elsevier]

Experimental studies show a drastic change of the characteristic features (Π-A isotherms, morphology of the condensed phase domains) of the 2C11H23-melamine monolayers by molecular recognition of the pyrimidine derivatives uracil and thymine, largely affected by the reaction kinetics of the recognition process. A new approximate additive theoretical model is introduced for describing the molecular recognition kinetics. The theoretical approach is based on two assumptions: (i) first-order reaction kinetics for the molecular recognition of the nonsurface active pyrimidine derivatives dissolved in the aqueous subphase by the melamine type monolayer and (ii) applicability of the Π-A isotherm equations derived previously for the description of melamine type monolayers in the fluid (gaseous, LE) state and the phase transition region to the condensed state. The rate constants for the molecular recognition reaction between the melamine type monolayer and the dissolved thymine and uracil are estimated, which are roughly proportional to the bulk concentrations of the pyrimidine derivatives and depend only slightly on the temperature. The theoretical estimates agree satisfactorily with the experimental results obtained under various conditions (Π = const and dA/dt = const). This fact supports the validity of the first model proposed for the interfacial molecular recognition kinetics with nonsurface active substrates dissolved in the aqueous subphase by complementary hydrogen bonding. [ABSTRACT FROM AUTHOR]

Abstract: Considering the deposition of charged Langmuir monolayers, it is necessary to take into account electrostatic interactions between the monolayer and the substrate surface. These interactions depend on the nature of ionizable surface groups and on the ionic composition of the subphase (e.g. pH, multivalent counterions, indifferent electrolytes). The non-uniformity of electric, concentration and hydrodynamic velocity fields leads to the formation of ion concentration profiles near the three-phase contact line during the deposition. This effect is similar to the effect of concentration polarization in membranes and electrode systems. The ions redistribution results in change of the monolayer ionization, adhesion work, dynamic contact angle, and, therefore, in the change of morphology, composition and structure of the deposited monolayer. With increasing withdrawal velocity the meniscus can become unstable because of concentration polarization in the solution. [Copyright &y& Elsevier]

Abstract: The effect of the OH-group position on the monolayer characteristics of hydroxypalmitic acids is studied by coupling the results of surface pressure–area (π–A) isotherm measurements and Brewster angle microscopy (BAM). In the present work, the phase behaviour and the domain morphology of 2-, 3- and 9-hydroxypalmitic acid monolayers are investigated. They deviate considerably but in different way from the adequate monolayer characteristics of the usual non-substituted amphiphiles. General differences exist also between the monolayer characteristics of palmitic acid OH-substituted near the COOH-group (in 2- or 3-position) and those when the OH-substitution is in or near the mid-position of the alkyl chain (in 9-position). This is demonstrated by differences in the temperature dependence of the phase transition pressure. The values of enthalpy and entropy change for the main phase transition are discussed and suggest in the case of 9-hyroxypalmitic acid, a structure improvement in the fluid monolayer phase at compression to the phase transition point because of reorientation into a perpendicular position. For the two types in the position of the OH-substitution, large differences in the morphology of the condensed phase domains indicate adequate differences in the long-range orientational order. In the case of OH-substitution near the COOH-head-group, irregular domain growth occurs while at OH-substitution in or near the mid-position of the alkyl chain, regular patterning of the domains indicate a high ordering. The reasons for the differences in the ordering are discussed. [Copyright &y& Elsevier]

Abstract: In the present work, the pair potential of enantiomeric N-palmitoyl aspartic acid amphiphile monolayer at the air/water interface is calculated based on an atomistic model. The molecular structure and partial charges are calculated using two semi empirical (PM3, AM1) and one empirical (Gasteiger and Marcili) methods. A distance-dependent dielectric function is used to represent the interfacial dielectric constant at the aqueous subphase. The present study indicates that a pair of molecules have favorable interaction at specific ranges of mutual orientations. Other orientations are favorable but at larger separations. Favorable electrostatic interaction at a specific combination of orientation and short separations of the head groups significantly contribute to the total energy. The curvature of the domain boundary is suggested to be driven by the favorable arrangement which is dependent on the pair potential of molecules. The use of charges obtained by the PM3 and GM do not lead to a significant variation of the orientation-dependent features, while the AM1 predicts higher partial charges and interactions are stronger than the former two methods. However, orientation-dependent features remain the same. The variations in the LJ parameters and charges indicate that the conclusions made are insensitive to the choice of parameters. The mutual favorable interaction predicted by calculation agree with the handedness of curvature of domains. [Copyright &y& Elsevier]

The new phenomenon of surface tension auto-oscillations can be initiated by using fatty acids as surface active substances. The oscillation characteristics of the adequate surfactant systems fatty acid–water and aliphatic alcohol–water having the same alkyl chain length, are compared. The results show that the buoyancy should be taken into account if the solubility of the surfactant is large enough and its density differs sufficiently from the density of water. In general, the behavior of the system fatty acid–water is more complicated than the earlier studied aliphatic alcohol–water systems. [Copyright &y& Elsevier]

In a short review, highlights of the progress in the understanding of the supramolecular organization in monolayers at the aqueous surface, mainly based on coupling of surface pressure measurements, Brewster angle microscopy studies and results of synchrotron X-ray diffraction at grazing incidence, are presented. Examples for the sensitive effect of the molecular structure of amphiphilic monolayers on the two-dimensional morphological texture, lattice structure, phase behaviour are discussed. New results on chiral discrimination effects, the existence of condensed phases in adsorbed monolayers, and the design of molecular recognition systems are reviewed. [Copyright &y& Elsevier]

The effect of chiral interaction on the morphology of the condensed phase domains of amino acid amphiphiles has been investigated theoretically in the present paper. The amphiphiles considered are N-palmitoyl aspartic acid, N-stearoyl serine methyl ester, N-palmitoyl-allo-threonine methyl ester and N-stearoyl-allo-threonine methyl ester. The domains of these amphiphiles show pronounced curvatures in the experiment, which are known to be driven by the chirality of the molecules concerned. We use the previously derived relations to calculate the intermolecular potential of a pair of chiral molecules of general shape, which is dependent on the intermolecular separation and the mutual orientation of the molecules. It is observed that the chiral interaction favors a mutual azimuthal orientation between the molecules in the unit cell for all amino acid amphiphiles considered. However, the azimuthal projections of the molecules within the domain are parallel as observed in the experiment. The energy to obtain parallel arrangement between the molecules is of the same order of the hydrogen bonding energy in the amino acid residues. Thus, it is suggested that the hydrogen bond cycles present among the molecules within the domain prevent the tendency of intermolecular twist due to chiral interaction. However, at the interface between the condensed phase and the fluid phase, the hydrogen bonding energy is not as strong as that within the domain as well as less direction specific. It is expected that the chiral interaction is dominating at the interface resulting the curved shape of the domain. The mutual orientation driven by chirality is cooperative in nature i.e. the mutual orientations at short and long axis of the unit cell occur in the same direction and does not oppose each other. The directions of the orientations of the molecules with respect to a reference molecule have the same senses (handedness) as those of the aggregates. The theoretically predicted senses of all four amino acid amphiphiles considered in the present study agree fairly well with the experimentally observed handedness using Brewster angle microscopy. [Copyright &y& Elsevier]

Due to the Angstrom resolution, Grazing incidence X-ray diffraction (GIXD) represents the most important technique for probing the lateral ordering in condensed monolayers at the air/water interface and allows the construction of phase diagrams of amphiphilic monolayers on the basis of two-dimensional lattice structures and tilt directions of the molecules. The high potential of GIXD is demonstrated by the structural characterization of a variety of amphiphilic monoalkanoylglycerol monolayers in Å-scale. The GIXD results have impressively shown that in the racemic 1-monostearoylglycerol monolayer with the appearance of an oblique intermediate phase (Obl) between the nearest neighbor (NN)- and next-nearest neighbor (NNN)-tilted orthorhombic phases symmetry breaking occurs at low temperatures. The generic lateral pressure−temperature phase diagram of racemic monoacylglycerol monolayers constructed on the basis of reliable two-dimensional lattice structures indicates that the new and surprising presence of the oblique phase depends only on the temperature. The significant effect of the substituted polar groups, chemical structure variations at the position of the glycerol backbone and chirality on the lattice structure in Å-scale was highlighted in a systematic overview on the structure and phase behavior of amphiphilic monoglycerol monolayers. The conspicuous effect of the position of the glycerol backbone at which the polar group is substituted is demonstrated. The monolayers of 2-monopalmitoyl-rac-glycerol behave as that of 1-monomyristoyl-rac-glycerol having a two CH 2 groups shorter alkyl chain. Further main topics discussed are chiral discrimination and crossover between homo- and heterochiral discrimination supported by quantum chemical calculations. Unlabelled Image • Use of Grazing incidence X-ray diffraction (GIXD) for probing the lateral ordering in condensed Langmuir monolayers. • Construction of generic phase diagrams of amphiphilic monoalkanoylglycerol monolayers. • Structural characterization of a variety of amphiphilic monoalkanoylglycerol monolayers in Å-scale. • Evidence for symmetry breaking in racemic monolayers. • An oblique intermediate phase (Obl) exists in racemic1-monostearoylglycerol at low temperatures. [ABSTRACT FROM AUTHOR]

The interplay between local, repulsive interactions and disorder acting only on one spin orientation of lattice fermions ("spin-dependent disorder") is investigated. The nonmagnetic disorder vs interaction phase diagram is computed using dynamical mean-field theory in combination with the geometric average over disorder. The latter determines the typical local density of states and is therefore sensitive to Anderson localization. The effect of spin-dependent disorder is found to be very different from that of conventional disorder. In particular, it destabilizes the metallic solution and leads to a spin-selective, localized phase at weak interactions and strong disorder. [ABSTRACT FROM AUTHOR]

Recent progress in modeling of the surfactant behavior from atomistic to continuous at the air/water interface across different space-time scales is reviewed. Advantages and disadvantages of modern quantum mechanical, molecular dynamical, and mesoscale methods are discussed for description of interactions between amphiphilic molecules leading to formation of 2D films. The use of nonempirical and semiempirical methods for assessment of the thermodynamic and structural parameters of large van der Waals complexes is of particular interest. An approach for calculation of the thermodynamic and structural parameters of clusterization for nonionic surfactants at the air/water interface is proposed on the basis of the quantum chemical semiempirical PM3 method. This approach implicitly takes into account the influence of the interface on the surfactant molecules via stretching and orienting effect. The calculations are carried out in the supermolecule approximation for a limited number of small amphiphilic aggregates with different alkyl chain. The correlation analysis of the calculated data array provides the increments contributing by the intermolecular CH · · · HC interactions and interactions between hydrophilic parts into the thermodynamic parameters of formation and clusterization. Obtained increments are further used for constructing the dependencies of the thermodynamic clusterization parameters per one monomer on the alkyl chain length for large clusters up to 2D films. In the framework of the proposed theoretical approach, the next parameters are calculated as follows: enthalpy, entropy, and Gibbs' energy of clusterization for 11 homologous series of nonionic surfactants, threshold chain length enabling the process of monolayer formation at standard conditions, the 'temperature effect' of clusterization, and the structural parameters of the monolayer unit cell (particularly the tilt angle) depending on the size of the hydrophilic headgroup of the amphiphilic compound. [ABSTRACT FROM AUTHOR]

We determine the electronic structure and phase stability of paramagnetic V2O3 at the Mott-Hubbard metal-insulator transition (MIT) by employing a combination of an ab initio method for calculating band structures with dynamical mean-field theory. The structural transformation associated with the MIT occurs upon a slight expansion of the lattice volume by ∼1.5%, in agreement with experiment. Our results show that the structural transition precedes the MIT, implying a complex interplay between electronic and lattice degrees of freedom. The MIT is found to be driven by a strong correlation-induced, orbital-selective renormalization of the V t2g bands. The effective electron mass of the eπg orbitals diverges at the MIT. Our results show that full charge self-consistency is crucial for a correct description of the physical properties of V2O3. [ABSTRACT FROM AUTHOR]

The temperature dependence of the paramagnetic susceptibility of the iron pnictide superconductor KFeAs and its connection with the spectral properties of that material is investigated by a combination of density functional theory (DFT) in the local density approximation and dynamical mean-field theory (DMFT). Unlike other iron pnictide parent compounds where the typical oxidation state of iron is 2, the formal valence of Fe in KFeAs is 2.5, corresponding to an effective doping with 0.5 hole per iron atom compared to, for example, BaFeAs. This shifts the chemical potential and thereby reduces the distance between the peaks in the spectral functions of KFeAs and the Fermi energy as compared to BaFeAs. The shift, which is clearly seen on the level of DFT as well as in DMFT, is further enhanced by the strong electronic correlations in KFeAs. In BaFeAs the presence of these peaks results (Phys. Rev. B 86, 125124 (2012)) in a temperature increase in the susceptibility up to a maximum at ∼1000 K. While the temperature increase was observed experimentally the decrease at even higher temperatures is outside the range of experimental observability. We show that in KFeAs the situation is different. Namely, the reduction of the distance between the peaks and the Fermi level due to doping shifts the maximum in the susceptibility to much lower temperatures, such that the decrease in the susceptibility becomes visible in experiment. [ABSTRACT FROM AUTHOR]

We introduce a novel computational approach for the investigation of complex correlated electron materials which makes it possible to evaluate interatomic forces and, thereby, determine atomic displacements and structural transformations induced by electronic correlations. It combines ab initio band structure and dynamical mean-field theory and is implemented with the linear-response formalism regarding atomic displacements. We apply this new technique to explore structural transitions of prototypical correlated systems such as elemental hydrogen, SrVO3, and KCuF3. [ABSTRACT FROM AUTHOR]

We analyze the sharpness of crossing ("isosbestic") points of a family of curves which are observed in many quantities described by a function f(x,p), where x is a variable (e.g., the frequency) and p is a parameter (e.g., the temperature). We show that if a narrow crossing region is observed near x. for a range of parameters p, then f(x,p) can be approximated by a perturbative expression in p for a wide range of x. This allows us, e.g., to extract the temperature dependence of several experimentally obtained quantities, such as the Raman response of HgBa2CuO4δ, photoemission spectra of thin VO2 films, and the reflectivity of CaCu3Ti4O12, all of which exhibit narrow crossing regions near certain frequencies. We also explain the sharpness of isosbestic points in the optical conductivity of the Falicov-Kimball model and the spectral function of the Hubbard model. [ABSTRACT FROM AUTHOR]

Employing a combination of ab initio band-structure theory and dynamical mean-field theory we explain the experimentally observed linear temperature increase of the magnetic susceptibility of the iron pnictide material BaFe2As2- The microscopic origin of this anomalous behavior is traced to a sharp peak in the spectral function located approximately 100 meV below the Fermi level. This peak is due to the weak dispersion of two-dimensional bands associated with the layered crystal structure of pnictides. [ABSTRACT FROM AUTHOR]

Abstract: Even though sodium dodecyl sulphate (SDS) is the most frequently studied surfactant, its properties at liquid interfaces are not easily accessible. This is mainly caused by the fact that in aqueous solution SDS is subject to hydrolysis, by which the homologous dodecanol (C12OH) is formed. Due to its enormously high surface activity it competes with SDS at the interface. We demonstrate here that this “natural” impurity C12OH does not remarkably affect the adsorption dynamics of SDS at the water/hexane interface, due to its high solubility in hexane. Therefore, the dynamic adsorption properties can be determined independent of disturbing dodecanol effects. The surfactant adsorbs diffusion controlled and the interfacial tension isotherm at the water/hexane interface is well described by a Frumkin model. However complementary experiments via direct admixture of dodecanol in hexane indicate a significant decrease in interfacial tension of the water–hexane interface at concentrations higher than 10−3 mol/l in hexane. This condition may happen when the oil phase is distributed as small droplets in a high concentrated solution of SDS. The distribution coefficient of C12OH between water and hexane is estimated from adsorption experiments to be Kp = co /cw =6.7×103. [ABSTRACT FROM AUTHOR]

Abstract: A simplified method is proposed to estimate the thermodynamic parameters of clusterization at the air/water interface for various classes of amphiphilic compounds with a single alkyl chain. The method is based on the calculation of thermodynamic characteristics only for one of the homologous series of dimers () governing the formation of infinite clusters. The method is used to calculate the thermodynamic parameters of clusterization for alcohols, thioalcohols, carboxylic acids and amines, and the dependencies of the Gibbs energy of clusterization on the alkyl chain length are evaluated. It is shown that the alkyl chain length, at which the spontaneous clusterization begins, as calculated using the proposed simplified method, is in fact the same as that calculated using the additive scheme developed earlier. The simplified method proposed was verified using alkylnitriles as example. In contrast to alcohols, thioalcohols and amines, infinite ‘rhombic’ clusters are formed rather than ‘rectangular’ clusters for this class of compounds. Spontaneous clusterization of nitriles is shown to start for alkyl chains containing 18–19 carbon atoms. This value agrees with that obtained from experimental data with 17–18 carbon atoms. The proposed simplified method introduces an exact and suitable tool for the estimation of thermodynamic parameters of the clusterization of amphiphilic compounds. [Copyright &y& Elsevier]

Abstract: The condensed phase monolayer domain forms interesting curvature due to chirality of the molecule. The handedness of d-N-palmitoyl aspartic acid is studied using the three-layered ONIOM (MO:MO:MM) model. Optimized structures of a pair of molecules are used to calculate the azimuthal projection of the molecular pairs. The pair of molecules shows a distinct minimum at the mutual azimuthal orientation corresponding to the left-handedness at the optimized separation. The other handedness is completely unfavorable. This is in nice agreement with the experimental data that d-enantiomer gives rise to left-handedness of the domains. Mutual large tilt between the molecules is also unfavored which is in agreement with the concept that molecules should not have large mutual tilt at the condensed phase. The energy surface gradually becomes flattened with increasing intermolecular separation. This is in agreement with the common wisdom that chirality induced effects decreases with increasing intermolecular separation. Present hybrid method based study reveals that the molecular chirality of the amphiphile can dictate the domain morphology in the condensed phase and is in agreement with experimental data and previous theoretical results based on effective pair potential theory and mechanics calculations. [Copyright &y& Elsevier]

The transition state of dimerization at the interface and between the initial and final clusterization products is analyzed. The calculations were performed using the PM3 molecular orbital approximation, implemented in the MOPAC 2000 software. It is shown that the account of the Gibbs energy ΔG leads to a saddle point at the potential energy surface for the two-dimensional cluster formation and re-clusterization in monolayers of normal fatty alcohols (n=8, 12, and 16). The re-organization of a linear trimer and monomer into two dimers was considered. The maximum value ΔG=110 kJ/mol for n-tetradecanol is observed for a distance of 10.5 Å which corresponds to the transition state of re-clusterization reaction. If the distance between the n-tetradecanol trimer and monomer is lower than 10.5 Å, then tetrameric clusters are formed again. For higher distances the monomer is detached from the trimer. The dependencies of the parameters of the activated complex corresponding to the alcohol dimerization reaction on the chain length are analyzed. The position of the maximum on the Gibbs energy curve for dimerization at 298 K corresponds to an intermolecular distances for the dimers in the transition state of 6.31–6.69 Å. [Copyright &y& Elsevier]

Auto-oscillations of the surface tension which are a new manifestation of the instability by the mass transfer in a two-component system, are considered. Experimental results for droplets of octanol and hexanol under a free water surface are presented as well as a theoretical explanation of the phenomena observed. Comparison of experimental results with those obtained by numerical simulation shows that the proposed model provides an adequate description of the system behaviour for middle-chain alcohols like octanol. The system behaviour is determined by matching between diffusion and Marangoni convection. For shorter chain alcohols like hexanol the buoyancy effect should be taken into account. [Copyright &y& Elsevier]

Langmuir-Blodgett (LB) multilayer systems are found to be inhomogeneous in morphology and structure. The most characteristic feature of these multilayer films is the appearance of three-dimensional domains in which the molecules arrange themselves as a result of the film transfer onto the substrate. A series of lead arachidate (PbA[SUB2]) LB multilayers have been prepared as model systems to study the dependence of film morphology on the pH value in the subphase. Atomic force microscopy (AFM) and two different x-ray scattering methods [specular (XSR) and diffuse (XDS) x-ray reflectometry] have been used to investigate the intrinsic interface properties, such as the vertical electron density profile and lateral distribution of head groups and chains, as well as the microscopic description of the interface structure, thus providing an overall picture of the investigated multilayers. With AFM, discrete height variations of domains with minimum step widths of one double layer independent of the salt concentration in the films were observed. The lateral domain size shows a dependence on pH. It was found to be maximum at pH = 4.2 (pure acid) but minimum at pH 7.0 (maximum salt content). The AFM pictures were treated by a statistical analysis to extract quantities that can be compared with the x-ray results. A considerable number of Bragg maxima were observed in XSR. The vertical correlation length L[SUBz] was calculated from the angular width of Bragg maxima along 2θ and was found to vary with pH value. It follows, in general, the tendency of the domain sizes, being maximum at pH = 4.8 and minimum at pH = 7.0, respectively. The lateral correlation length L[SUBx] has been evaluated via XDS from the half widths Δω measured by rocking the sample across a fixed 2θ. It decreases for increasing pH. L[SUBx] was compared with the respective quantity of the AFM analysis. Estimated by XDS, the correlation lengths for inner interfaces and domains... [ABSTRACT FROM AUTHOR]

The thermodynamic and structural parameters of monolayers of N -alkanoyl-substituted alanine with 8–17 methylene fragments in the alkyl chain are calculated on the basis of the quantum chemical semiempirical PM3 method. Four optimized structures of monomers are obtained. The energetically most preferred conformer is used for construction of dimers with “sequential” and “parallel” orientation of the hydrophilic parts of the monomers and tetramers with square structure. The hydrophobic chains of N -alkanoyl-substituted alanine are found to be inclined in the dimers to the normal of the spread monolayer: δ = 10° and φ = 43°. Comparison of clusterization Gibbs’ energy for small clusters suggests that 2D film formation takes place by formation of linear associates comprised of dimers with “parallel” orientation of the hydrophilic groups. The temperature increase causes growth of linear 1D clusters leading to the dendritic structure of the monolayer. The parameters of the unit cell of 2D film are calculated: a = 4.65 Ǻ, b = 6.20 Ǻ, the angle between the sides of the cell θ = 105˚. The tilt angle of amphiphilic molecules to the normal of the air/water interface is t = 47°. The calculated parameters of the unit cell are in good agreement with the existing experimental data. The spontaneous clusterization threshold for N -alkanoyl-substituted alanine at the air/water interface is calculated to be 15 carbon atoms in the chain at 288 K. This is only 2 carbon atoms more than the experimental value and within the margin of error of the model used for the calculation. [ABSTRACT FROM AUTHOR]

We present results of a detailed theoretical study of the electronic, magnetic, and structural properties of the chalcogenide parent system FeSe using a fully charge-self-consistent implementation of the density functional theory plus dynamical mean-field theory (DFT+DMFT) method. In particular, we predict a remarkable change of the electronic structure of FeSe which is accompanied by a complete reconstruction of the Fermi surface topology (Lifshitz transition) upon a moderate expansion of the lattice volume. The phase transition results in a change of the in-plane magnetic nesting wave vector from (π,π) to (π,0) and is associated with a transition from itinerant to orbital-selective localized magnetic moments. We attribute this behavior to a correlation-induced shift of the Van Hove singularity of the Fe t2 bands at the M point across the Fermi level. Our results reveal a strong orbital-selective renormalization of the effective mass m*/m of the Fe 3d electrons upon expansion. The largest effect occurs in the Fe xy orbital, which gives rise to a non-Fermi-liquid-like behavior above the transition. The behavior of the momentum-resolved magnetic susceptibility χ(q) demonstrates that magnetic correlations are also characterized by a pronounced orbital selectivity, suggesting a spin-fluctuation origin of the nematic phase of paramagnetic FeSe. We conjecture that the anomalous behavior of FeSe upon expansion is associated with the proximity of the Fe t2 Van Hove singularity to the Fermi level and the sensitive dependence of its position on external conditions. [ABSTRACT FROM AUTHOR]

Materials with correlated electrons often respond very strongly to external or internal influences, leading to instabilities and states of matter with broken symmetry. This behavior can be studied theoretically either by evaluating the linear response characteristics, or by simulating the ordered phases of the materials under investigation. We developed the necessary tools within the dynamical mean-field theory (DMFT) to search for electronic instabilities in materials close to spin-state crossovers and to analyze the properties of the corresponding ordered states. This investigation, motivated by the physics of LaCoO, led to a discovery of condensation of spinful excitons in the two-orbital Hubbard model with a surprisingly rich phase diagram. The results are reviewed in the first part of the article. Electronic correlations can also be the driving force behind structural transformations of materials. To be able to investigate correlation-induced phase instabilities we developed and implemented a formalism for the computation of total energies and forces within a fully charge self-consistent combination of density functional theory and DMFT. Applications of this scheme to the study of structural instabilities of selected correlated electron materials such as Fe and FeSe are reviewed in the second part of the paper. [ABSTRACT FROM AUTHOR]

In the framework of the model for surfactant clusterization description at the air/liquid and liquid/liquid interfaces proposed earlier (Vysotsky et al. J. Phys. Chem. B, 2015, 119 (7), 3281–3296) and based on the quantum chemical semi-empirical PM3 method the structural and thermodynamic parameters of the formation of 1-( N -alkyl)-imidazole monolayers with alkyl chain lengths of 6–16 carbon atoms at the air/water interface are calculated. The model allows the calculation of the thermodynamic parameters (enthalpy, entropy and the Gibbs’ energy) of monomers, clusters and monolayers at the interface between two liquids or between the air and liquid phases. To obtain such results one needs to calculate the corresponding thermodynamic parameters for both adjacent phases within the semi-empirical PM3 method (in the frameworks of the COSMО procedure), then to calculate the increments from the different types of the pairwise interactions and, with the help of the additive scheme, to calculate the required parameters. It has been shown that 1-( n -alkyl)-imidazole forms monolayers with hexagonal and oblique unit cells normal conditions. The parameters of the unit cell are calculated for each of these monolayers: 4.6 Ǻ and 7.2 Ǻ (the angle γ between the sides of the unit cell is equal to 62°) for the hexagonal unit cells and 4.6 Ǻ and 4.6 Ǻ ( γ = 80°) for the oblique unit cells. Enthalpy, entropy and Gibbs’ energy for small clusters (dimers–hexamers), representing the structural elements of the investigated monolayers, are calculated. The probable way of the clusterization process is proposed on the basis of these parameters. In the framework of the model the thermodynamic functions of the monolayer formation are calculated. These results indicate that for both types of the monolayers (with oblique and hexagonal unit cells) spontaneous clusterization is possible when the alkyl chain length is ≥14–15 carbon atoms. [ABSTRACT FROM AUTHOR]

The electronic structure and phase stability of paramagnetic FeSe is computed by using a combination of ab initio methods for calculating band structure and dynamical mean-field theory. Our results reveal a topological change (Lifshitz transition) of the Fermi surface upon a moderate expansion of the lattice. The Lifshitz transition is accompanied with a sharp increase of the local moments and results in an entire reconstruction of magnetic correlations from the in-plane magnetic wave vector, (π, π) to (π, 0). We attribute this behavior to a correlation-induced shift of the van Hove singularity originating from the dxy and dxz/dyz bands at the M point across the Fermi level. We propose that superconductivity is strongly influenced, or even induced, by a van Hove singularity. [ABSTRACT FROM AUTHOR]

We present theoretical results on the high-temperature phase stability and phonon spectra of paramagnetic bcc iron which explicitly take into account many-body effects. Several peculiarities, including a pronounced softening of the [110] transverse (T1) mode and a dynamical instability of the bcc lattice in harmonic approximation are identified. We relate these features to the α-to-γ and γ-to-δ phase transformations in iron. The high-temperature bcc phase is found to be highly anharmonic and appears to be stabilized by the lattice entropy. [ABSTRACT FROM AUTHOR]

Motivated by the rapidly growing possibilities for experiments with ultracold atoms in optical lattices, we investigate the thermodynamic properties of correlated lattice fermions in the presence of an external spindependent random potential. The corresponding model, a Hubbard model with spin-dependent local random potentials, is solved within dynamical mean-field theory. This allows us to present a comprehensive picture of the thermodynamic properties of this system. In particular, we show that for a fixed total number of fermions spin-dependent disorder induces a magnetic polarization. The magnetic response of the polarized system differs from that of a system with conventional disorder. [ABSTRACT FROM AUTHOR]

Abstract: The superposition-additive approach developed previously was shown to be applicable for the calculations of the thermodynamic parameters of formation and atomization of conjugate systems, their dipole polarizability, molecular diamagnetic susceptibility, π-electronic ring currents, etc. In the present work, the applicability of this approach for the calculation of the thermodynamic parameters of formation and clusterization at the water/air interface of alkanes, fatty alcohols, thioalcohols, amines, nitriles, fatty acids (C n H2 n +1X, X is the functional group) and cis-unsaturated carboxylic acids (C n H2 n −1COOH) is studied. Using the proposed approach the thermodynamic quantities determined agree well with the available data, either calculated using the semiempirical (PM3) quantum chemical method, or obtained in experiments. In particular, for enthalpy and Gibbs’ energy of the formation of substituted alkane monomers from the elementary substances, and their absolute entropy, the standard deviations of the values calculated according to the superposition-additive scheme with the mutual superimposition domain C n −2H2 n −4 (n is the number of carbon atoms in the alkyl chain) from the results of PM3 calculations for alkanes, alcohols, thioalcohols, amines, fatty acids, nitriles and cis-unsaturated carboxylic acids are respectively: 0.05, 0.004, 2.87, 0.02, 0.01, 0.77, and 0.01kJ/mol for enthalpy; 2.32, 5.26, 4.49, 0.53, 1.22, 1.02, 5.30J/(molK) for absolute entropy; 0.69, 1.56, 3.82, 0.15, 0.37, 0.69, 1.58kJ/mol for Gibbs’ energy, whereas the deviations from the experimental data are: 0.52, 5.75, 1.40, 1.00, 4.86kJ/mol; 0.52, 0.63, 1.40, 6.11, 2.21J/(molK); 2.52, 5.76, 1.58, 1.78, 4.86kJ/mol, respectively (for nitriles and cis-unsaturated carboxylic acids experimental data are not available). The proposed approach provides also quite accurate estimates of enthalpy, entropy and Gibbs’ energy of boiling and melting, critical temperatures and standard heat capacities for several classes of substituted alkanes. For the calculation of thermodynamic functions of clusterization of dimers, trimers and tetramers of fatty alcohols, thioalcohols, amines, carboxylic acids and cis-unsaturated carboxylic acids two superposition-additive schemes are proposed which ensure the correct superimposition of the molecular graphs, including intermolecular hydrogen–hydrogen interactions in the clusters. The calculations involve the thermodynamic parameters of clusterization obtained earlier by the PM3 method. It is shown that the proposed approach reproduces quite accurately the values calculated earlier and is applicable for the prediction of the thermodynamic parameters of the formation of surfactant monolayers. [Copyright &y& Elsevier]

Abstract: The superposition-additive approach developed earlier was shown to be applicable for the calculations of the thermodynamic parameters of formation and atomisation of conjugate systems, their dipole polarisability, molecular diamagnetic susceptibility, π-electronic ring currents etc. In this publication, the applicability of this approach for the calculation of the thermodynamic parameters (enthalpy and Gibbs’ energy of formation from elementary substances, and absolute entropy) of alkanes, fatty alcohols, thioalcohols, amines, nitriles, fatty carboxylic acids and nitriles with the general composition C n H2n+1X (X is the functional group) is studied. It is shown that the thermodynamic quantities determined using the proposed approach agree to within the satisfactory precision with the available calculated and experimental data. [Copyright &y& Elsevier]

Abstract: A simple method for estimation of the 2D spontaneous clusterization temperature of substituted alkanes at the air/water interface versus alkyl chain length is proposed using the quantum chemical semiempirical PM3 method. The method is approved by long-chain amines, alcohols, thioalcohols, saturated and unsaturated carboxylic acids, α-amino acids and amides of carboxylic acids. The method is based on the experimental fact that short chain amphiphilic molecules cannot form condensed 2D monolayers whereas above a specific alkyl chain length condensed monolayer phases can be observed under the same conditions. That is, elongation of the alkyl chain of amphiphilic molecules causes the increase of intermolecular interaction energy between them what stimulates their close packing and structuring. This leads to linear or stepwise dependencies of enthalpy and entropy of cluster formation on the alkyl chain length. It is possible to obtain an equation for the estimation of the temperature of the spontaneous clusterization threshold of the considered substituted alkane types by setting Gibbs’ energy equal to zero and by knowing the regression expressions for determination of enthalpy and entropy of cluster formation calculated under the condition of 298K using coefficients which determine the contribution of the hydrophilic head group interactions of molecules and CH⋯HC-interactions between the alkyl chains. It is shown that the temperature dependence of the spontaneous clusterization threshold on the alkyl chain length of the amphiphile is fractionally linear with a relative error of 3–8%. The effect of the alkyl chain elongation of substituted alkanes by two methylene units corresponds to subphase temperature reduction (ΔТ) by 10–20K in good agreement with the available experimental data. The difference between ΔТ values for considered types of amphiphilic compounds becomes less significant with the lengthening of the alkyl chain. This indicates the basic contribution of intermolecular CH⋯HC-interactions between the alkyl chains to the process of the 2D clusterization. [Copyright &y& Elsevier]

An approach to calculation of the threshold temperaturefor spontaneous clusterization of substituted alkanes (amines, nitriles,alcohols, thioalcohols, saturated and unsaturated carboxylic acids,α-amino acids, carboxylic acid amides, and melamine derivatives)at the air/water interface with dependence on the alkyl chain lengthwas developed. In the framework of this approach, four schemes forthe description of the temperature dependencies of the thermodynamicparameters of clusterization of the concerned amphiphilic compoundswere proposed. They use the data obtained previously in the frameworkof quantum chemical semiempirical PM3 method and differ from eachother by the degree of their theoretical accuracy. It was shown thatthe threshold temperature for spontaneous clusterization of the regardedclasses of substituted alkanes can be described using a fractionallylinear function in dependence on the alkyl chain length. It was foundthat, in agreement with the presented experimental data, the effectof the alkyl chain elongation of the substituted alkanes by two methyleneunits correlates with the decrease of the subphase temperature (ΔT) by 10–20 K. The general shape of the obtaineddependencies indicates that the difference in the ΔTvalues for the amphiphilic molecules decreases with increasing alkylchain length. This implies that the contribution of the intermolecularCH···HC interactions between the alkyl chains of monolayermolecules should be a decisive factor. [ABSTRACT FROM AUTHOR]