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The stochastic density functional theory (DFT) [R. Baer et al., Phys. Rev. Lett. 111, 106402 (2013)] is a valuable linear-scaling approach to Kohn-Sham DFT that does not rely on the sparsity of the density matrix. Linear (and often sub-linear) scaling is achieved by introducing a controlled statistical error in the density, energy, and forces. The statistical error (noise) is proportional to the inverse square root of the number of stochastic orbitals and thus decreases slowly; however, by dividing the system into fragments that are embedded stochastically, the statistical error can be reduced significantly. This has been shown to provide remarkable results for non-covalently-bonded systems; however, the application to covalently bonded systems had limited success, particularly for delocalized electrons. Here, we show that the statistical error in the density correlates with both the density and the density matrix of the system and propose a new fragmentation scheme that elegantly interpolates between overlapped fragments. We assess the performance of the approach for bulk silicon of varying supercell sizes (up to Ne = 16 384 electrons) and show that overlapped fragments reduce significantly the statistical noise even for systems with a delocalized density matrix. [ABSTRACT FROM AUTHOR]

The third view of space states that space is neither lifeless nor neutral, but a living structure capable of being more living or less living. The living structure is defined as a physical and mathematical structure or simply characterized by the recurring notion (or the inherent hierarchy) of far more small substructures than large ones. The more substructures the more living, and the higher hierarchy of the substructures the more living. This paper seeks to lay out a new kind of GeoInformatics on the notion of living structure and on the third view of space. The new GeoInformatics aims not only to better understand the forms and processes of everyday space but also-maybe more importantly-to make the space or the Earth's surface living or more living. We introduce two fundamental laws of living structure : Tobler's law on spatial dependence or homogeneity and scaling law on spatial interdependence or heterogeneity. We further argue that these two laws favor statistics over exactitude, because the statistics tend to make a structure more living than the exactitude. We present the concept of living structure through some working examples and make it clear how a living structure differs from a non-living or less-living structure. In order to make a structure or space living or more living, we introduce two design principles-differentiation and adaptation-using two paintings and two city plans as working examples. The new GeoInformatics is a science of living structure, dealing with a wide range of scales of the everyday space, from the smallest scale of ornaments on walls to the scale of the entire Earth's surface. [ABSTRACT FROM AUTHOR]

Near the Curie temperature, the anisotropy field of magnetically uniaxial L10 FePt is expected to follow the scaling law (1 – T/Tc)β, where T is the temperature and Tc is the Curie temperature. In the literature, β values between 0.36 and 0.65 have been reported. Based on recording measurements and micromagnetic analysis, we show that only the values of β near the low end of the reported range are compatible with the data. We also conclude that thermally activated magnetization reversal at temperatures near Tc cannot be ignored, even at time scales smaller than 1 ns. We demonstrate that thermally activated magnetization reversal at temperatures close to Tc is well described by conventional theory with a frequency factor f0 of the order of 1012 Hz. It is reasoned that the unusually high value for f0 is a consequence of the temperature-induced reduction of the degree of alignment of the micro-spins within the grains. [ABSTRACT FROM AUTHOR]

The mathematical structure imposed by the thermodynamic critical point motivates an approximant that synthesizes two theoretically sound equations of state: the parametric and the virial. The former is constructed to describe the critical region, incorporating all scaling laws; the latter is an expansion about zero density, developed from molecular considerations. The approximant is shown to yield an equation of state capable of accurately describing properties over a large portion of the thermodynamic parameter space, far greater than that covered by each treatment alone. [ABSTRACT FROM AUTHOR]

In this study 2d two phase microstructures closely resembling the experimentally captured micrographs of the interpenetrating phase composites are generated using a Gaussian correlation function based method. The scale dependent bounds on the effective thermal conductivity of such microstructures are then studied using Hill-Mandel boundary conditions. A scaling function is formulated to describe the transition from statistical volume element (SVE) to representative volume element (RVE), as a function of the mesoscale δ, the correlation length of the Gaussian correlation function λ, the volume fraction v, and the contrast k between the phases. The scaling function is determined through fitting the data from extensive simulations conducted over the parameter space. The scaling function shows that SVE approaches RVE as (δ/λ)-1.16. A material scaling diagram allows estimation of the RVE size, to within a chosen accuracy, of a given microstructure characterized by the correlation length of the Gaussian correlation function, contrast, and volume fraction of the phases. [ABSTRACT FROM AUTHOR]

The performance of correlated optimized effective potential (OEP) functionals based on the spinresolved second-order correlation energy is analysed. The relative importance of singly- and doublyexcited contributions as well as the effect of scaling the same- and opposite- spin components is investigated in detail comparing OEP results with Kohn-Sham (KS) quantities determined via an inversion procedure using accurate ab initio electronic densities. Special attention is dedicated in particular to the recently proposed scaled-opposite-spin OEP functional [I. Grabowski, E. Fabiano, and F. Della Sala, Phys. Rev. B 87, 075103 (2013)] which is the most advantageous from a computational point of view. We find that for high accuracy, a careful, system dependent, selection of the scaling coefficient is required. We analyse several size-extensive approaches for this selection. Finally, we find that a composite approach, named OEP2-SOSh, based on a post-SCF rescaling of the correlation energy can yield high accuracy for many properties, being comparable with the most accurate OEP procedures previously reported in the literature but at substantially reduced computational effort. [ABSTRACT FROM AUTHOR]

Detail observation of human locations became available recently by the development of information technology such as mobile phones with GPS (Global Positioning System). We analyzed temporal changes of global human flow patterns in urban regions based on mobile phones' GPS data in 9 large cities in Japan. By applying a new concept of drainage basins in analogous to river flow patterns, we discovered several universal scaling relations. These include, the number of moving people in a drainage basin of diameter L is proportional to L 3 in the morning rush hour, which is surprisingly different from reasonable intuition of proportionality to the 2 dimensional area, L 2 . We show that this unexpected 3 dimensional feature is related to the strong attraction of the city center to become a 3 dimensional structure due skyscrapers. [ABSTRACT FROM AUTHOR]

The Hayabusa2 spacecraft investigated the small asteroid Ryugu, which has a rubble-pile structure. We describe an impact experiment on Ryugu using Hayabusa2's Small Carry-on Impactor. The impact produced an artificial crater with a diameter >10 meters, which has a semicircular shape, an elevated rim, and a central pit. Images of the impact and resulting ejecta were recorded by the Deployable CAMera 3 for >8 minutes, showing the growth of an ejecta curtain (the outer edge of the ejecta) and deposition of ejecta onto the surface. The ejecta curtain was asymmetric and heterogeneous and it never fully detached from the surface. The crater formed in the gravity-dominated regime; in other words, crater growth was limited by gravity not surface strength. We discuss implications for Ryugu's surface age. [ABSTRACT FROM AUTHOR]

The number of aftershocks increases with mainshock size following a well-defined scaling law. However, excursions from the average behavior are common. This variability is particularly concerning for large earthquakes where the number of aftershocks varies by factors of 100 for mainshocks of comparable magnitude. Do observable factors lead to differences in aftershock behavior We examine aftershock productivity relative to the global average for all mainshocks (MW > 6.5) from 1990 to 2019. A global map of earthquake productivity highlights the influence of tectonic regimes. Earthquake depth, lithosphere age, and plate boundary type correspond well with earthquake productivity. We investigate the role of mainshock attributes by compiling source dimensions, radiated seismic energy, stress drop, and a measure of slip heterogeneity based on finite-fault source inversions for the largest earthquakes from 1990 to 2017. On an individual basis, stress drop, normalized rupture width, and aspect ratio most strongly correlate with aftershock productivity. A multivariate analysis shows that a particular set of parameters (dip, lithospheric age, and normalized rupture area) combines well to improve predictions of aftershock productivity on a cross-validated data set. Our overall analysis is consistent with a model in which the volumetric abundance of nearby stressed faults controls the aftershock productivity rather than variations in source stress. Thus, we suggest a complementary approach to aftershock forecasts based on geological and rupture properties rather than local calibration alone. [ABSTRACT FROM AUTHOR]

In this paper, a total of 5 Dense Plasma Focus (DPF) machines, working in argon gas which uses Mather type anode (7 energy range), were analysed using numerical experimentation (Lee Codes). Three important scaling laws relating the all line yield to the peak current, pinch current and energy input into the plasma were obtained. The scaling laws act as guidelines in scaling the DPF for applications such as medical radiation. [ABSTRACT FROM AUTHOR]

The scaling behaviors of dynamic ferroelectric hysteresis in the relaxor ferroelectric 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (PMNT67/33) ceramics near the morphotropic phase boundary (MPB) and other PMNT systems out of MPB region were investigated. The scaling relation of hysteresis area against frequency f and field amplitude E0 for minor loops takes the form of ∝f-0.2391E04.8779; while for the saturated loops, it is ∝f 0.0401E00.5722. The scaling relations of PMNT67/33 ceramics are significantly different from those of other ferroelectrics, and the results of the analysis indicate that domain reversal in it is much more sensitive to the change of E0 at low electric field and responses more quickly to f at high electric field than other normal ferroelectrics. The coexistence of rhombohedral (R), monoclinic (M) and tetragonal (T) phases near the MPB and the polar nanoregions seems to play the key role in the dynamic behavior of the domain reversal in relaxor PMNT67/33 ceramics. [ABSTRACT FROM AUTHOR]

The dynamics of atomic force microscopy (AFM) microcantilevers in liquid environments have been previously shown to be extremely complex and nonlinear, exhibiting phenomena such as momentary excitation of higher eigenmodes, fluid-borne excitation, mass loading, and the emergence of sub-harmonic responses. It has also been shown that the signals acquired by the instrument can differ significantly between tip- and base-excited cantilevers in highly damped environments, such that it can be difficult for users to modulate the peak impact forces for base-excited AFM systems that are not equipped with advanced force spectroscopy tools. Despite the dynamic complexity, we show that through understanding of simple scaling laws based on the damped harmonic oscillator model and operation at high amplitude setpoints, it is possible to modulate the tip-sample forces, which could be useful in studies that require experiments involving different but controllable peak force levels. [ABSTRACT FROM AUTHOR]

This study establishes that the effective thermal conductivity keff of crystalline nanoporous silicon is strongly affected not only by the porosity fν and the system's length Lz but also by the pore interfacial area concentration Ai. The thermal conductivity of crystalline nanoporous silicon was predicted using non-equilibrium molecular dynamics simulations. The Stillinger-Weber potential for silicon was used to simulate the interatomic interactions. Spherical pores organized in a simple cubic lattice were introduced in a crystalline silicon matrix by removing atoms within selected regions of the simulation cell. Effects of the (i) system length ranging from 13 to 130 nm, (ii) pore diameter varying between 1.74 and 5.86 nm, and (iii) porosity ranging from 8% to 38%, on thermal conductivity were investigated. A physics-based model was also developed by combining kinetic theory and the coherent potential approximation. The effective thermal conductivity was proportional to (1 - 1.5fν) and inversely proportional to the sum (Ai/4 + 1/Lz). This model was in excellent agreement with the thermal conductivity of nanoporous silicon predicted by molecular dynamics simulations for spherical pores (present study) as well as for cylindrical pores and vacancy defects reported in the literature. These results will be useful in designing nanostructured materials with desired thermal conductivity by tuning their morphology. [ABSTRACT FROM AUTHOR]

Here, we propose a new complex path to achieve better absorption during the propagation of a wavepacket. In the proposed modified smooth exterior scaling (SES) method, scaling function, θ(x), has been chosen as a real function rather than complex (as used in a conventional smooth exterior scaling method). It greatly reduces the artificial reflections from the boundary edges. This modified SES method is applied to study the multiphoton dissociation of H2+ in intense laser field. The resonance states are calculated accurately. [ABSTRACT FROM AUTHOR]

Computer simulations are used to test whether a recently introduced generalization of Rosenfeld's excess-entropy scaling method for estimating transport coefficients in systems obeying molecular dynamics can be extended to predict long-time diffusivities in fluids of particles undergoing Brownian dynamics in the absence of interparticle hydrodynamic forces. Model fluids with inverse-power-law, Gaussian-core, and Hertzian pair interactions are considered. Within the generalized Rosenfeld scaling method, long-time diffusivities of ultrasoft Gaussian-core and Hertzian particle fluids, which display anomalous trends with increasing density, are predicted (to within 20%) based on knowledge of interparticle interactions, excess entropy, and scaling behavior of simpler inverse-power-law fluids. [ABSTRACT FROM AUTHOR]

The regime of validity of Rosenfeld excess entropy scaling of diffusivity and viscosity is examined for two tetrahedral, network-forming ionic melts (BeF2 and SiO2) using molecular dynamics simulations. With decrease in temperature, onset of local caging behavior in the diffusional dynamics is shown to be accompanied by a significant increase in the effect of three-body and higher-order particle correlations on the excess entropy, diffusivity, ionic conductivity, and entropy-transport relationships. The signature of caging effects on the Rosenfeld entropy scaling of transport properties is a distinctly steeper dependence of the logarithm of the diffusivity on the excess entropy in ionic melts. This is shown to be true also for a binary Lennard-Jones glassformer, based on available results in the literature. Our results suggest that the onset of a landscape-influenced regime in the dynamics is correlated with this characteristic departure from Rosenfeld scaling. The breakdown of the Nernst-Einstein relation in the ionic melts can also be correlated with the emerging cooperative dynamics. [ABSTRACT FROM AUTHOR]

The thermodynamic properties of a simple fluid confined by effective wall forces are calculated using Monte Carlo simulations in the grand canonical ensemble. The solvation force produced by polymer brushes of two different lengths is obtained also. For the particular type of model interactions used, known as the dissipative particle dynamics method, we find that it is possible to obtain an exact, simple expression for the effective force induced by a planar wall composed of identical particles that interact with those in the fluid. We show that despite the short range of all forces in the model, the solvation force can be finite at relatively large distances and therefore does not depend only on the range of the interparticle or solvent-surface forces. As for the polymer brushes, we find that the shape of the solvation force profiles is in fair agreement with scaling and self-consistent field theories. The applications and possible extensions of this work are discussed. [ABSTRACT FROM AUTHOR]

The regime of validity of Rosenfeld excess entropy scaling of diffusivity and viscosity is examined for two tetrahedral, network-forming ionic melts (BeF2 and SiO2) using molecular dynamics simulations. With decrease in temperature, onset of local caging behavior in the diffusional dynamics is shown to be accompanied by a significant increase in the effect of three-body and higher-order particle correlations on the excess entropy, diffusivity, ionic conductivity, and entropy-transport relationships. The signature of caging effects on the Rosenfeld entropy scaling of transport properties is a distinctly steeper dependence of the logarithm of the diffusivity on the excess entropy in ionic melts. This is shown to be true also for a binary Lennard-Jones glassformer, based on available results in the literature. Our results suggest that the onset of a landscape-influenced regime in the dynamics is correlated with this characteristic departure from Rosenfeld scaling. The breakdown of the Nernst-Einstein relation in the ionic melts can also be correlated with the emerging cooperative dynamics. [ABSTRACT FROM AUTHOR]

We present a detailed study of the heating effects in dielectric measurements carried out on a liquid. Such effects come from the dissipation of the electric power in the liquid and give contribution to the nonlinear third harmonics susceptibility χ3, which depends on the frequency and temperature. This study is used to evaluate a possible 'spurious' contribution to the recently measured nonlinear susceptibility of an archetypical glassforming liquid (glycerol). Those measurements have been shown to give a direct evaluation of the number of dynamically correlated molecules temperature dependence close to the glass transition temperature Tg≈190 K [Crauste-Thibierge et al., Phys. Rev. Lett. 104, 165703 (2010)]. We show that the heating contribution is totally negligible (i) below 204 K at any frequency; (ii) for any temperature at the frequency where the third harmonics response χ3 is maximum. Besides, this heating contribution does not scale as a function of f/fα, with fα(T) the relaxation frequency of the liquid. In the high frequency range, when f/fα≥1, we find that the heating contribution is damped because the dipoles cannot follow instantaneously the temperature modulation due to the heating phenomenon. An estimate of the magnitude of this damping is given. [ABSTRACT FROM AUTHOR]

Constituting the simplest generalization of spherical Coulomb crystals, assemblies of N equicharged particles confined by radial potentials proportional to the λth power of distance are amenable to rigorous analysis within the recently introduced shell model. Thanks to the power scaling of the confining potential and the resulting pruning property of the shell configurations (i.e., the lists of shell occupancies), the shell-model estimates of the energies and the mean radii of such assemblies at equilibrium geometries follow simple recursive formulas. The formulas greatly facilitate derivations of the first two leading terms in the large-N asymptotics of these estimates, which are given by power series in ξ4/3 N-2/3, where -(ξ/2) n3/2 is the leading angular-correlation correction to the minimum energy of n electrons on the surface of a sphere with a unit radius (the solution of the Thomson problem). Although the scaled occupancies of the outermost shells conform to a universal scaling law, the actual filling of the shells tends to follow rather irregular patterns that vary strongly with λ. However, the number of shells K(N) for a given N decreases in general upon an increase in the power-law exponent, which is due to the (λ+1)2 ξ2 dependence of shell capacities that roughly measure the maximum numbers of particles sustainable within individual shells. Several types of configuration transitions (i.e., the changes in the number of shells upon addition of one particle) are observed in the crystals with up to 10 000 particles and integer values of λ between 1 and 10, but the rule |K(N + 1) - K(N)| <= 1 is found to be strictly obeyed. [ABSTRACT FROM AUTHOR]

The translocation of α-helix chains through a nanopore is studied through Langevin dynamics simulations. The α-helix chains exhibit several different characteristics about their average translocation times and the α-helix structures when they transport through the nanopores under the driving forces. First, the relationship between average translocation times τ and the chain length N satisfies the scaling law, τ∼Nα, and the scaling exponent α depends on the driving force f for the small forces while it is close to the Flory exponent (ν) in the other force regions. For the chains with given chain lengths, it is observed that the dependence of the average translocation times can be expressed as τ∼f-1/2 for the small forces while can be described as τ∼f in the large force regions. Second, for the large driving force, the average number of α-helix structures Nh decreases first and then increases in the translocation process. The average waiting time of each bead, especially of the first bead, is also dependent on the driving forces. Furthermore, an elasticity spring model is presented to reasonably explain the change of the α-helix number during the translocation and its elasticity can be locally damaged by the large driving forces. Our results demonstrate the unique behaviors of α-helix chains transporting through the pores, which can enrich our insights into and knowledge on biopolymers transporting through membranes. [ABSTRACT FROM AUTHOR]

We report calculations on three classes of knotted ring polymers: (1) simple-cubic lattice self-avoiding rings (SARs), (2) “true” theta-state rings, i.e., SARs generated on the simple-cubic lattice with an attractive nearest-neighbor contact potential (θ-SARs), and (3) ideal, Gaussian rings. Extrapolations to large polymerization index N imply knot localization in all three classes of chains. Extrapolations of our data are also consistent with conjectures found in the literature which state that (1) Rg→ANν asymptotically for ensembles of random knots restricted to any particular knot state, including the unknot; (2) A is universal across knot types for any given class of flexible chains; and (3) ν is equal to the standard self-avoiding walk (SAW) exponent (≅0.588) for all three classes of chains (SARs, θ-SARs, and ideal rings). However, current computer technology is inadequate to directly sample the asymptotic domain, so that we remain in a crossover scaling regime for all accessible values of N. We also observe that Rg∼p-0.27, where p is the “rope length” of the maximally inflated knot. This scaling relation holds in the crossover regime, but we argue that it is unlikely to extend into the asymptotic scaling regime where knots become localized. [ABSTRACT FROM AUTHOR]

We have calculated the hydrodynamic radius Rh and intrinsic viscosity [η] of both lattice self-avoiding rings and lattice theta-state rings that are confined to specific knot states by our path-integration technique. We observe that naive scaling arguments based on the equilibrium polymer size fail for both the hydrodynamic radius and the intrinsic viscosity, at least over accessible chain lengths. (However, we do conjecture that scaling laws will nevertheless prevail at sufficiently large N.) This failure is attributed to a “double” cross-over. One cross-over effect is the transition from delocalized to localized knotting: in short chains, the knot is distributed throughout the chain, while in long chains it becomes localized in only a portion of the chain. This transition occurs slowly with increasing N. The other cross-over, superimposed upon the first, is the so-called “draining” effect, in which transport properties maintain dependence on local structure out to very large N. The hydrodynamic mobility of knotted rings of the same length and backbone structure is correlated with the average crossing number X of the knots. The same correlation between mobility and knot complexity X has been observed for the gel-electrophoretic mobility of cyclic DNA molecules. [ABSTRACT FROM AUTHOR]

Symmetry-adapted perturbation theory (SAPT) offers insight into the nature of intermolecular interactions. In addition, accurate energies can be obtained from the wave function-based variant of SAPT provided that intramonomer electron correlation effects are included. We apply density-fitting (DF) approximations to the intramonomer correlation corrections in SAPT. The introduction of this approximation leads to an improvement in the computational cost of SAPT by reducing the scaling of certain SAPT terms, reducing the amount of disk I/O, and avoiding the explicit computation of certain types of MO integrals. We have implemented all the intramonomer correlation corrections to SAPT through second-order under the DF approximation. Additionally, leading third-order terms are also implemented. The accuracy of this truncation of SAPT is tested against the S22 test set of Hobza and co-workers [Phys. Chem. Chem. Phys. 8, 1985 (2006)]. When the intramonomer corrections to dispersion are included in SAPT, a mean absolute deviation of 0.3–0.4 kcal mol-1 is observed for the S22 test set when using an aug-cc-pVDZ basis. The computations on the adenine-thymine complexes in the S22 test set with an aug-cc-pVDZ basis represent the largest SAPT computations to date that include this degree of intramonomer correlation. Computations of this size can now be performed routinely with our newly developed DF-SAPT program. [ABSTRACT FROM AUTHOR]

Coupled cluster calculations can be carried out for large molecular systems via a set of calculations that use small orbital fragments of the full molecular orbital space. The error in the correlation energy of the full molecular system is controlled by the precision in the small fragment calculations. The determination of the orbital spaces for the small orbital fragments is black box in the sense that it does not depend on any user—provided molecular fragmentation, rather orbital spaces are carefully selected and extended during the calculation to give fragment energies of a specified precision. The computational method scales linearly with the size of the molecular system and is massively parallel. [ABSTRACT FROM AUTHOR]

Excess entropy scaling relationships for diffusivity of ions in room-temperature ionic liquids are tested using molecular dynamics simulations for a model ionic liquid, dimethyl imidazolium chloride. The thermodynamic excess entropy of the single ions (estimated from the ion-ion pair correlation functions) is shown to be very strongly correlated with the diffusivity. An essential feature of these systems, the fact that the heavier and larger cation has a greater diffusivity with respect to the anion, is correctly captured by the excess entropy calculations, which estimates the diffusivity ratio between the two ions with noticeable precision. [ABSTRACT FROM AUTHOR]

Using Monte Carlo simulations and finite-size scaling analysis, the critical behavior of attractive rigid rods of length k (k-mers) on square lattices at intermediate density has been studied. A nematic phase, characterized by a big domain of parallel k-mers, was found. This ordered phase is separated from the isotropic state by a continuous transition occurring at a intermediate density θc. Our study allowed us (1) to determine the dependence of θc on the size of the rods and the magnitude of the lateral interactions and (2) to obtain the critical exponents, which indicate that the transition belongs to the 2D Ising universality class. [ABSTRACT FROM AUTHOR]

We compute the partition function of self-avoiding chains tethered inside a confining sphere using Monte Carlo simulations on a three-dimensional lattice. Two cases are considered: (i) single-tethered chains with one end anchored and one end free and (ii) double-tethered chains where both ends are tethered at a distance equal to the diameter of the sphere. The self-avoidance, confinement, and tethering constraints dramatically decrease the number of allowed configurations when compared with an unconstrained random coil, thereby affecting the sampling method used in the Monte Carlo procedure. The effect of an external applied force and the bias it introduces in the partition function are also investigated. Our method involves a decomposition of the partition function into the product of several terms that can be evaluated independently. For short chains, we demonstrate the validity of our approach through a direct evaluation of the partition function using an exact enumeration of the appropriate paths on the lattice. In the case of long chains, scaling laws for the behavior of the partition function are identified. [ABSTRACT FROM AUTHOR]

On approaching the glass transition, the microscopic kinetic unit spends increasing time rattling in the cage of the first neighbors, whereas its average escape time, the structural relaxation time τα, increases from a few picoseconds up to thousands of seconds. A thorough study of the correlation between τα and the rattling amplitude, expressed by the Debye–Waller factor, was carried out. Molecular-dynamics simulations of both a model polymer system and a binary mixture were performed by varying the temperature, the density ρ, the potential and the polymer length to consider the structural relaxation as well as both the rotational and the translation diffusion. The present simulations, together with MD studies on other glassformers, evidence the scaling between the structural relaxation and the caged dynamics. An analytic model of the master curve is developed in terms of two characteristic length scales a2 1/2 and σa21/2, pertaining to the distance to be covered by the kinetic unit to reach a transition state. The model does not imply τα divergences. The comparison with the experiments supports the numerical evidence over a range of relaxation times as wide as about eighteen orders of magnitude. A comparison with other scaling and correlation procedures is presented. In particular, the density scaling of the length scales a2 1/2, σa21/2∝ρ-1/3 is shown to be not supported by the present simulations. The study suggests that the equilibrium and the moderately supercooled states of the glassformers possess key information on the huge slowing-down of their relaxation close to the glass transition. The latter, according to the present simulations, exhibits features consistent with the Lindemann melting criterion and the free-volume model. [ABSTRACT FROM AUTHOR]

Dynamic scaling behavior has been observed during the room-temperature growth of sputtered Pd films on SiO2 using the scanning electron microscopy technique. By the analyses of the dependence of the Pd grain size and surface density on the film thickness, the dynamical growth exponent z=4.2±0.3 was obtained, suggesting a conservative growth process. The analysis of the fraction of surface covered by Pd as a function of film thickness (up to a maximum of 8.5×1016 atoms/cm2, corresponding to 125 nm) allowed us to identify two different growth regimes in the investigated range: films thinner than 1.8×1016 atoms/cm2 (26.5 nm) that grow as an outside-cluster system and thicker film that exhibit an islandlike growth. [ABSTRACT FROM AUTHOR]

Dynamic scaling behavior has been observed during the room-temperature growth of sputtered Pd films on SiO2 using the scanning electron microscopy technique. By the analyses of the dependence of the Pd grain size and surface density on the film thickness, the dynamical growth exponent z=4.2±0.3 was obtained, suggesting a conservative growth process. The analysis of the fraction of surface covered by Pd as a function of film thickness (up to a maximum of 8.5×1016 atoms/cm2, corresponding to 125 nm) allowed us to identify two different growth regimes in the investigated range: films thinner than 1.8×1016 atoms/cm2 (26.5 nm) that grow as an outside-cluster system and thicker film that exhibit an islandlike growth. [ABSTRACT FROM AUTHOR]

Dissipative particle dynamics (DPD) is now a well-established method for simulating soft matter systems. However, its applicability was recently questioned because some investigations showed an upper coarse-graining limit that would prevent the applicability of the method to the whole mesoscopic range. This article aims to re-establish DPD as a truly mesoscopic method by analyzing the problems reported by other authors and by presenting a scaling scheme that allows one to apply DPD simulations directly to any desired length scale. [ABSTRACT FROM AUTHOR]

Acid-treated and pristine chemical vapor deposition grown multiwalled carbon nanotube (MWNT) and poly(bisphenol A carbonate) (PC) composites were prepared through a simple solution blending with varied nanotube weight fractions. The electrical conductivities of the composites can be described by the scaling law based on percolation theory with unprecedented high saturated ac conductivity of pristine nanotubes (σsat=1598.4 S cm-1, pc=0.19 wt %) and acid-treated nanotubes (σsat=435.4 S cm-1, pc=0.3 wt %), which correlates well with the dc behavior. We attribute the high saturated conductivities to managing the dispersions, rather than looking to have a well dispersed three-dimensional network thin film. The comparison was made between acid-treated nanotubes and pristine nanotube, both dispersed in PC at various loadings. It was found that the pristine nanotubes in PC possessed an even higher conductivity than the more evenly dispersed composites consisting of lightly acid-treated MWNT in PC. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations were employed in models of peripherally charged dendrimers in solutions of explicit solvent and monovalent counterions in order to explore aspects of the dynamic behavior of counterions. The present study explores the effects of varying strength of electrostatic interactions for models of two dendrimer generations, in explicit solvent solutions below the dendrimer overlap concentration. Counterion diffusional motion as well as residence lifetimes of pairs formed by charged dendrimer beads and condensed counterions is monitored in the different electrostatic regimes. Spatiotemporal characteristics of self- and collective counterion motion are explored by means of space-time Van Hove correlation functions. A characteristic scaling law is found to describe the counterion diffusion coefficient as a function of Bjerrum length in the strong electrostatic regime, independent of the size of the dendrimer molecules at the examined volume fractions. The change noted in the diffusional motion of counterions in the range of strong Coulombic interactions is also reflected to their relevant residence times. Development of dynamic heterogeneities in counterion self-motion is observed during the gradual increase in the strength of electrostatic interactions, characterized by the emergence of distinct counterion populations in terms of their mobility. The time scale for the development of such a mobility contrast in the self-motion of the counterions can be correlated with that describing their collective motion as well. The latter increases with Bjerrum length but remains shorter compared to the time scale at which free diffusional motion sets in. Findings from the present study provide further insight on the mechanisms pertinent to ion migration in macroion dispersions and may serve as a basis for the interpretation of ionic motion in a broader range of polyelectrolyte systems. [ABSTRACT FROM AUTHOR]

The periodicity of 180° stripe domains has been calculated analytically by assuming a linear change in magnetization/polarization in the domain wall. A modified scaling law was proposed between the domain period and the film thickness for ferroelectric and ferromagnetic thin films. Both the slope and intercept of this scaling line can be used to get domain wall thickness in a consistent manner, which enriches the understanding of domain walls. Theoretical results have been used to compare with recent experimental data and suggest a good agreement. [ABSTRACT FROM AUTHOR]

Thin nanostructured gold films were deposited on SiO2 by the sputtering technique at room temperature. Films of different thicknesses were deposited ranging from 2 to 16 nm. The film morphology as a function of the thickness was analyzed by microscopic techniques such as atomic force microscopy and transmission electron microscopy. These analyses allowed us to clarify the growth mechanism of the gold nanograins forming the film: in a first stage of growth (2–6 nm) normal grain growth proceeds; then (8–16 nm) the grain surface energy anisotropy drives the growth of abnormal large gold grains by annihilation of the normal ones. During the abnormal growth other normal grain continue to growth. The normal grain size distribution is showed to be a monomodal log-normal distribution that evolves toward larger mean grain radius continuously following a scaling law. By determination of the grain growth exponent, the kinetic mechanism responsible of the grain growth is demonstrated to be the gold atomic diffusion on grain boundaries. By fitting the experimental data using established theoretical models, the room-temperature gold grain boundary coefficient diffusion and mobility were derived. The abnormal grain grows, manifest itself as a bimodal grain size distribution: with the log-normal distribution of the normal grain size, a second Gaussian grain size distribution rises, shifting toward lower size increasing the film thickness. The abnormal grain growth continues until all the abnormal grain boundaries meet each other. [ABSTRACT FROM AUTHOR]

We present results obtained using dimensional scaling with high-frequency Floquet theory to evaluate the stability of gas phase simple diatomic molecules in superintense laser fields. The large-D limit provides a simple model that captures the main physics of the problem, which imposes electron localization along the polarization direction of the laser field. This localization markedly reduces the ionization probability and can enhance chemical bonding when the laser strength becomes sufficiently strong. We find that energy and structure calculations at the large-dimensional limit (D→∞) for stabilities of H2+, H2, and He2 in superintense laser fields are much simpler than at D=3, yet yield similar results to those found from demanding ab initio calculations. We also use the large-D model to predict the stability of H2- and the field strength needed to bind the “extra” electron to the H2 molecule. [ABSTRACT FROM AUTHOR]

Exploiting the high angular resolution of high field electron paramagnetic resonance measured at 95, 190, and 285 GHz we determine the rotational nonergodicity parameter of different probe molecules in the glass former o-terphenyl and polybutadiene in a model-independent way. Our results clearly show a characteristic change in the temperature of the nonergodicity parameter proving a rather sharp dynamic crossover in both systems, in contrast to previous results from other techniques. [ABSTRACT FROM AUTHOR]

We investigate acceptor and donor states in GaN nanocrystals doped with a single substitutional impurity. Quantum dots (QDs) of zinc-blende structure and spherical shape are considered with radius ranging from 4.5 to 67.7 Å. The size-dependent energy spectra are calculated within the sp3d5s* tight-binding model, which yields a good agreement with the confinement-induced blueshifts observed in undoped QDs. The computed binding energy is strongly enhanced with respect to the experimental bulk value when the dopant is placed at the center of the smallest QDs. It decreases with increasing QD size following a scaling law that extrapolates to the bulk limit. In order to estimate the degree of localization of the bound carriers, we analyze their wave functions and average radii. The resulting physical picture points to a highly localized acceptor hole, mostly distributed over the nearest-neighbor anion shell, and a much more extended donor electron. We also study off-center impurities in intermediate-sized QDs. The acceptor binding energy is approximately independent of the dopant position unless it is placed within a surface shell of thickness of the order of the bulk Bohr radius, where the ionization energy abruptly drops. On the contrary, the donor binding energy gradually decreases as the impurity is moved away from the center toward the QD surface. [ABSTRACT FROM AUTHOR]

We present a theoretical analysis of the scaling of the polarization and the static dielectric susceptibility through a mean-polarization approach for ultrathin epitaxial PbZrxTi1-xO3 thin films. We use the traditional Euler-Lagrangian framework applied to a Landau-Ginzburg-Devonshire (LGD) nonlinear thermodynamic treatment. The novelty of our approach is that the model hinges on using experimentally measured correlation lengths and temperature scaling relationships to give the size-dependent expansion parameters of the nonlinear thermodynamic potential. These are then used in a Taylor series expansion of the polarization at the center of the film. We show that this method is able to correctly predict experimentally observed scaling without the need for the so-called extrapolation length (which is impossible to measure experimentally). Furthermore, as no implicit correlation between the correlation length (ξ) and the coefficient of the gradient term in the LGD potential (g11) is assumed, the model thus involves fully experimentally measurable parameters and their systematic temperature dependence rather than implicit assumptions. The model finds that the Curie temperature in ultrathin films is more sensitive to epitaxial strain as compared to the polarization and that the critical thickness is strongly dependent on the “temperature-epitaxial strain” parameter space. Interestingly, while it finds that at lower temperatures the depolarization field does play a strong role in the thickness dependence as well as spatial profile of the polarization, with increasing temperature, a significant weakening of the role of depolarization fields occurs. Consequently the interface-induced suppression is lower and, as a result, the polarization profile is more homogenous at higher temperatures. This indicates that systematic temperature dependent studies are fundamental to further understanding of size effects in ferroelectrics. [ABSTRACT FROM AUTHOR]

The recently introduced method of correlation energy extrapolation by intrinsic scaling (CEEIS) is used to calculate the nonrelativistic electron correlations in the valence shell of the F2 molecule at 13 internuclear distances along the ground state potential energy curve from 1.14 Å to 8 Å, the equilibrium distance being 1.412 Å. Using Dunning’s correlation-consistent double-, triple-, and quadruple-zeta basis sets, the full configuration interaction energies are determined, with an accuracy of about 0.3 mhartree, by successively generating up to octuple excitations with respect to multiconfigurational reference functions that strongly change along the reaction path. The energies of the reference functions and those of the correlation energies with respect to these reference functions are then extrapolated to their complete basis set limits. The applicability of the CEEIS method to strongly multiconfigurational reference functions is documented in detail. [ABSTRACT FROM AUTHOR]

We demonstrate the scaling properties of the gate-bias-dependent transfer characteristics of In2O3 nanowire field effect transistors (FETs) studied using a conducting atomic force microscope. The contact resistance was extracted from the scaling of the resistance of an In2O3 nanowire FET with respect to its channel length. This contact resistance was found to be significant for short channel devices and decreased as the gate bias increased. We also investigated the apparent and intrinsic mobilities of the nanowire FET as a function of channel length and gate bias. It was determined that the intrinsic mobility could be corrected by considering the non-negligible contact resistance. [ABSTRACT FROM AUTHOR]

We present a computationally inexpensive method that yields ground state wave functions of pure spin symmetry. The method is variational and rigorously size consistent, free from adjustable parameters, and has a favorable scaling with system size. It is based on the recently introduced partially spin restricted geminal wave functions with limited spin contamination. Computations of a bond breaking, a transition metal compound, and a symmetric hydrogen cluster confirm the properties of this method. [ABSTRACT FROM AUTHOR]

We have studied the longitudinal electronic collective transport properties in a disordered array of TiSi2 nanocrystals (with surface density of 1012 cm-2) embedded in Si polycrystalline matrix as a function of temperature. The system is characterized by a high degree of disorder compared to the standard disordered nanocrystal array usually studied in the literature. Despite of this fundamental difference, we demonstrate that the theoretical models used to describe the collective electronic transport in standard systems are adequate to describe the electrical behavior of such a “nonstandard” system. In particular, we show that two different conduction regimes, separated by a crossover temperature T*, exist: at T

We have simulated silicon nanowire field effect transistors in the ballistic transport regime using the effective mass theory and the mode space nonequilibrium Green’s function method. In order to solve the two-dimensional Schrödinger equations on the nanowire cross-sectional planes as a part of the numerical procedure, we have developed an efficient numerical scheme, the product-space method, where the size of the eigenvalue problem is reduced to the number of subband modes that participate in the transport. We have investigated the scaling behavior of the nanowire transistors and found that their device characteristics sensitively depend on the aspect ratio of the channel length and width. [ABSTRACT FROM AUTHOR]

We investigate theoretically the dynamics of a colloidal particle, trapped by optical tweezers, which gradually approaches an attractive surface with a constant velocity until it escapes the trap and jumps to the surface. We find that the height of the energy barrier in such a colloid-surface system follows the scaling ΔE∝(z0(t)-const)3/2 when the trap approaches the surface, z0(t) being the trap surface distance. Using this scaling we derive equations for the probability density function of the jump lengths, for the velocity dependence of its mean and most probable values, and for the variance. These can be used to extract the parameters of the particle-surface interaction from experimental data. [ABSTRACT FROM AUTHOR]

We present a cellular automaton (CA) model of particles in a single-file motion with free particle exchange at the boundaries of a one-dimensional channel connected to two infinite reservoirs in order to study the self-transmission of particles with excluded mutual passage. The parallel, local and homogeneous rule sets of the CA algorithm consider two different interactions of varying strength between particles, without any specific particle-channel interaction. CA model results suggest that one hallmark of single-file motion is the conduction bursts at a particular time scale, which have thus far only been discovered for hydrogen bond networked water translocation. The cumulative transport probabilities of particles through single-file channels of different length follow a single profile, which can be obtained through proper scaling of time. The universal features of our results suggest new experiments in single-file channel with fluids other than water. [ABSTRACT FROM AUTHOR]

The scaling laws of transport properties are very important for understanding the transport mechanisms of the fractal-like tree networks, which have received extensive attention recently. In this paper, we analyze the transport properties including electrical conductivity, heat conduction, convective heat transfer, laminar flow, and turbulent flow in the networks and also derive the scaling exponents of the transport properties in the networks. We show that the scaling laws are different for different transport processes and the scaling exponents are sensitive to microstructures of the networks. The models and results we present here may shed light on the transport mechanisms of the networks such as the natural systems, nanotube networks, microelectronic cooling networks, organisms, fracture networks in oil/water reservoirs, seepage flow in porous networks/media, etc., and might provide guidance for design of composites with the tree structures. [ABSTRACT FROM AUTHOR]

Monte Carlo simulation has been used to investigate the effects of linear solvent molecular size on polymer chain conformation in solutions. Increasing the solvent molecular size leads to shrinkage of the polymer chains and increase of the critical overlap concentrations. The root-mean-square radius of gyration of polymer chains (Rg) is less sensitive to the variation of polymer concentration in solutions of larger solvent molecules. In addition, the dependency of Rg on polymer concentration under normal solvent conditions and solvent molecular size is in good agreement with scaling laws. When the solvent molecular size approaches the ideal end-to-end distance of the polymer chain, an extra aggregation of polymer chains occurs, and the solvent becomes the so-called medium-sized solvent. When the size of solvent molecules is smaller than the medium size, the polymer chains are swollen or partially swollen. However, when the size of solvent molecules is larger than the medium size, the polymer coils shrink and segregate, enwrapped by the large solvent molecules. [ABSTRACT FROM AUTHOR]