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Integral equation theory calculations within the mean spherical approximation (MSA) and grand canonical Monte Carlo (MC) simulations are employed to study the phase behaviour of a symmetrical binary fluid mixture in the presence of a field arising from unequal chemical potentials of the two particle species. Attention is focused on the case for which, in the absence of a field, the phase diagram exhibits a first order liquid-liquid transition in addition to the liquid-vapor transition. We find that in the presence of a field, two possible subtypes of phase behaviour can occur, these being distinguished by the relationship between the critical lines in the full phase diagram of temperature, density, and concentration. We present the detailed form of the respective phase diagrams as calculated from MSA and compare with results from the MC simulations, finding good overall agreement., 8 pages, 2 figures

In an effort to approach a quantitative determination of the phase diagram of polydisperse mixtures of (possibly size-asymmetric) charged hard spheres (CHS), we propose a concept that explicitly takes into account the association of the ions into dimers, i.e., an effect that is known to be of high relevance close to the liquid-vapor phase boundary in the restricted primitive model (RPM). We use the polymer mean spherical approximation (PMSA) to calculate the properties of this polydisperse mixture of dimers. The concept turns out to be a truncatable free energy model, thus the phase diagram can be calculated by solving a highly non-linear set of equations. We present the full phase diagram (in terms of cloud and shadow curves and binodals) and discuss fractionation effects for a model system.

A review is given on recent studies of charged colloidal suspensions and polyelectrolytes both in static and non-equilibrium situations. As far as static equilibrium situations are concerned, we discuss three different problems: 1) Sedimentation density profiles in charged suspensions are shown to exhibit a stretched non-bariometric wing at large heights and binary suspensions under gravity can exhibit an analog of the brazil-nut effect known from granular matter, i.e. the heavier particles settle on top of the lighter ones. 2) Soft polyelectrolyte systems like polyelectrolyte stars and microgels show an ultra-soft effective interaction and this results into an unusual equilibrium phase diagram including reentrant melting transitions and stable open crystalline lattices. 3) The freezing transition in bilayers of confined charged suspensions is discussed and a reentrant behaviour is obtained. As far as nonequilibrium problems are concerned, we discuss an interface instability in oppositely driven colloidal mixtures and discuss possible approaches to simulate electrokinetic effects in charged suspensions.

It is by now well established that the self-consistent Ornstein-Zernike approximation (SCOZA) is able to provide accurate data for the location of the liquid-vapour coexistence curve and for the critical point of simple fluids. However, up to now applications of the SCOZA were restricted only to a rather small variety of interatomic potentials. In this contribution we present an extension of the SCOZA which offers access to a considerably larger class of systems. As an example, we present results for model fullerenes Cn ≥ 60 (characterised by the sphericalized Girifalco potentials) and thus contribute to the still open question on the existence of the liquid phase and on the size of the liquid pocket in the phase diagram of fullerenes.

We develop a density functional for hard-sphere mixtures which keeps the structure of Rosenfeld's fundamental measure theory (FMT) whilst inputting the Mansoori–Carnahan–Starling–Leland bulk equation of state. Density profiles for the pure hard-sphere fluid and for some binary mixtures adsorbed at a planar hard wall obtained from the present functional exhibit some improvement over those from the original FMT. The pair direct correlation function c(2) (r) of the pure hard-sphere fluid, obtained from functional differentiation, is also improved. When a tensor weight function is incorporated for the pure system our functional yields a good description of fluid–solid coexistence and of the properties of the solid phase.

We test the accuracy of a recently proposed density functional (DF) for a fluid in contact with a porous matrix. The DF was constructed in the spirit of Rosenfeld’s fundamental measure concept and was derived for general mixtures of hard core and ideal particles. The required double average over fluid and matrix configurations is performed explicitly. As an application we consider am odel mixture where colloids and matrix particles are represented by hard spheres and polymers by ideal spheres. Integrating over the degrees of freedom of the polymers leads to a binary colloid–matrix system with effective Asakura– Oosawa pair potentials, which we treat with an integral-equation theory. We fin dt hat partial pair correlation functions from both theories are in good agreement with our computer simulation results, and that the theoretical results for the demixing binodals compare well, provided the polymer-to-colloid size ratio, and hence the effect of many-body interactions neglected in the effective model, is not too large. Consistently, we find that hard (ideal) matrix–polymer interactions induce capillary condensatio n( evaporation) of the colloidal liquid phase.

It has become clear that the self-consistent Ornstein–Zernike approximation (SCOZA) is a microscopic liquid-state theory that is able to predict the location of the critical point and of the liquid–vapour coexistence line of a simple fluid with high accuracy. However, applications of the SCOZA to continuum systems have been restricted up to now to liquids where the interatomic potentials consist of a hard-core part with an attractive two-Yukawa-tail part. We present here a reformulation of the SCOZA that is based on the Wertheim–Baxter formalism for solving the mean-spherical approximation for a hard-core–multi-Yukawa-tail fluid. This SCOZA version offers more flexibility and opens access to systems where the interactions can be represented by a suitable linear combination of Yukawa tails. We demonstrate the power of this generalized SCOZA for a model system of fullerenes; furthermore, we study the critical behaviour of a system with an explicitly density-dependent interaction where the phenomenon of double criticality is observed. Finally, we extend our SCOZA version to the case of a binary symmetric mixture and present and discuss results for phase diagrams.

Our investigations of the phase diagram of a symmetric binary fluid in equilibrium with a porous matrix show that moderate changes in the properties of the matrix or in the matrix-fluid interaction lead to drastic modifications of the phase diagram of the fluid. Thus our results confirm on a qualitative basis recent experimental data. The phase diagrams that we have obtained show a wide variation and can be classified in terms of archetypes of systems of two order parameters. These different types can be characterised in terms of the loci where the λ-line of the demixing transition intersects the first-order liquid-vapour coexistence curve. Results are based on the optimised random phase approximation and on grand-canonical Monte Carlo simulations.

We have reinvestigated the structural and thermodynamic properties of the square-well and the square-shoulder system using two different theoretical frameworks, i.e., the optimized random-phase approximation and the Rogers-Young integral equation. We discuss the limits of applicability of the respective concepts and compare the results with `exact' Monte Carlo simulation results and with data obtained from a semi-analytic method proposed by Nezbeda for narrow wells. Using these correlation functions, we study in the framework of the modified-weighted-density approximation the isostructural solid-solid transition predicted for narrow wells and narrow shoulders.

We show that a microscopic generalization of the Stokes - Einstein relation between the diffusion and shear viscosity coefficients, previously tested in simple liquids near melting, has a much wider range of application. The practical validity of the approach is accurately checked by performing extensive computer simulations in liquid sodium at temperatures ranging from 403 K to 1003 K.

We have extended an integral-equation approach (proposed by Winn and Logan, and, in parallel, by Stratt and co-workers) for the determination of the electronic density of states of disordered materials within the 'tight-binding' framework to the case of an sp 3 model. This formalism leads to a set of coupled complex-valued integral equations which turn out to be formally equivalent to the Onrstein-Zernike equations of an ion-dipole mixture. As a closure relation, which is required for the solution, we have used a linear relation. In order to check the reliability of this approach we have complemented the integral-equation data with results from a 'tight-binding' molecular-dynamics simulation. As an example we chose liquid silicon, using the 'tight-binding' parametrization proposed by Goodwin et al. The agreement of the two sets of data is very satisfactory.

A recently introduced algorithm for solving the inverse problem for simple classical fluids (i.e. the deduction of the interatomic interaction from structural data), which is based on the fundamental-measure free-energy density functional for hard spheres, is analysed in comparison with other methods. In a benchmark test for the Lennard-Jones system near the triple point, it is comparable with about ten simulations in the iterative predictor - corrector scheme proposed some years ago by Levesque, Weis, and Reatto. The method is used to extract the effective pair potential of Kr from very accurate experimental neutron scattering structure factor data.

We have studied the structure and dynamics of liquid lithium (pure 7Li) in a computer experiment: the states (470, 526 and 573K) correspond exactly to those investigated recently in neutron scattering experiments by Verkerk and co-workers. Instead of a potential based on a simple local pseudopotential which is usually sufficient for the alkali metals we have used a potential which is based on a non-local OPW-pseudopotential. Both single-particle and collective correlation functions have been calculated. For all temperatures we achieve very good agreement for the total dynamic structure factor. Also the diffusion constant, the specific heat at constant volume and the adiabatic velocity of sound extracted from our data are in good agreement with the experimentally determined values.

A recently developed method due to Winn and Logan (and in a similar formulation by Xu and Stratt) allows the determination of the electronic density of states (DOS) of disordered systems by solving a generalized, complex-valued Ornstein-Zernike-type equation. The only input required is the pair distribution function (characterizing the structure of the disordered system) and the transfer matrix element. A closure relation, necessary for the solution has been proposed by the authors: it is derived-assuming some approximations-from an originally exact relation. Up to now this method has only been applied to model systems, where an exact analytical solution of the equations was possible. For this study the authors have solved the integral equation along with the closure relation numerically. For the pair interaction of the particles they have considered both hard-core and continuous potentials; various transfer-matrix elements have been used. The results for the DOS have been compared to molecular-dynamics results, where the electronic DOS has been determined by direct diagonalization of the tight-binding Hamiltonian: they find the agreement between the numerical results and the simulation data to be good. Differences may be attributed to the approximations made in the derivation of the closure relation.

The authors present explicit formulae which allow an economical but very accurate evaluation of the pair-distribution functions gij(r) for the whole range of distances of an additive binary hard-sphere system within the Percus-Yevick approximation. The method is based on the fact that for such a system the Laplace-transforms gij(t) of the gij(r) are known analytically. The inversion of the Laplace-transform is performed in two different ways: the first one-preferably applied from the contact up to distances of a few diameters-calculates the inverse by means of an exact analytical procedure, whereas the other one-very useful for intermediate and large distances-uses an asymptotic method, truncating a rapidly converging series expansion. In the overlap region of the two methods they obtain perfect agreement (i.e. up to machine precision), including the first few terms of this expansion. Both formulae are presented as general as possible to allow for an easy extension to other binary hard-core systems.

We use monomer-resolved numerical simulations to study the positional and orientational structure of a dense dendrimer solution, focusing on the effects of dendrimers' prolate shape and deformability on the short-range order. Our results provide unambiguous evidence that the nearest-neighbor shell of a tagged particle consists of a mixture of crossed, side-by-side, side-to-end, and end-to-end pair configurations, imposing antinematic rather than nematic order observed in undeformable rodlike particles. This packing pattern persists even at densities where particle overlap becomes sizable. We demonstrate that the antinematic arrangement is compatible with the A15 crystal lattice reported in several dendrimer compounds., 6 pages, 3 figures

We have investigated diffusion and hopping processes in a cluster crystal formed from mesoscopic, ultrasoft particles. In contrast to previous contributions we have explicitly included in our investigations the microscopic solvent by using a simulation scheme that takes the induced hydrodynamic interactions into account as faithfully as possible. In our investigations we first focused on the processes of migration of the ultrasoft particles. By evaluating dynamical correlation functions we were able to demonstrate that the presence of the solvent does indeed have an important impact on the diffusion and hopping processes of the particles: this applies in particular to the diffusive behaviour, to the angular orientation of the jump events and to the spatial extents of these events. In a second set-up we have added non-cluster-forming ultrasoft particles to the system, investigating thus the impact of the solvent and that of the mutual interaction of the two species of ultrasoft particles on their respective dynamic behaviours. Our investigations clearly demonstrate, beside the expected significant role that the solvent plays in this set-up, that diffusion and the jump processes show distinct differences for the two particle species. (Some figures may appear in colour only in the online journal)

The Eighth Liquid Matter Conference (LMC8) was held at the Universität Wien from 6-10 September 2011. Initiated in 1990, the conferences of this series cover a broad range of highly interdisciplinary topics, ranging from simple liquids to soft matter and biophysical systems. The vast spectrum of scientific subjects presented and discussed at the LMC8 is reflected in the themes of the ten symposia: Ionic and quantum liquids, liquid metals Water, solutions and reaction dynamics Liquid crystals Polymers, polyelectrolytes, biopolymers Colloids Films, foams, surfactants, emulsions, aerosols Confined fluids, interfacial phenomena Supercooled liquids, glasses, gels Non-equilibrium systems, rheology, nanofluids Biofluids, active matter This special issue contains scientific papers, authored by participants of the LMC8, which provide a cross-section of the scientific activities in current liquid matter science, as discussed at the conference, and demonstrate the scientific as well as methodological progress made in this field over the past couple of years. The Eighth Liquid Matter Conference contents The Eighth Liquid Matter ConferenceChristoph Dellago, Gerhard Kahl and Christos N Likos Comparing light-induced colloidal quasicrystals with different rotational symmetriesMichael Schmiedeberg and Holger Stark Hydrogen bond network relaxation in aqueous polyelectrolyte solutions: the effect of temperatureS Sarti, D Truzzolillo and F Bordi Equilibrium concentration profiles and sedimentation kinetics of colloidal gels under gravitational stressS Buzzaccaro, E Secchi, G Brambilla, R Piazza and L Cipelletti The capillary interaction between two vertical cylindersHimantha Cooray, Pietro Cicuta and Dominic Vella Hydrodynamic and viscoelastic effects in polymer diffusionJ Farago, H Meyer, J Baschnagel and A N Semenov A density-functional theory study of microphase formation in binary Gaussian mixturesM Carta, D Pini, A Parola and L Reatto Microcanonical determination of the interface tension of flat and curved interfaces from Monte Carlo simulationsA Tröster and K Binder Phase diagrams of particles with dissimilar patches: X-junctions and Y-junctionsJ M Tavares and P I C Teixeira The unbearable heaviness of colloids: facts, surprises, and puzzles in sedimentationRoberto Piazza, Stefano Buzzaccaro and Eleonora Secchi Exploring water and other liquids at negative pressureFrédéric Caupin, Arnaud Arvengas, Kristina Davitt, Mouna El Mekki Azouzi, Kirill I Shmulovich, Claire Ramboz, David A Sessoms and Abraham D Stroock The configurational space of colloidal patchy polymers with heterogeneous sequencesIvan Coluzza and Christoph Dellago Repeated sorption of water in SBA-15 investigated by means of in situ small-angle x-ray scatteringM Erko, D Wallacher, G H Findenegg and O Paris Transition of the hydration state of a surfactant accompanying structural transitions of self-assembled aggregatesM Hishida and K Tanaka The effects of topology on the structural, dynamic and mechanical properties of network-forming materialsMark Wilson Surface tension of an electrolyte-air interface: a Monte Carlo studyAlexandre Diehl, Alexandre P dos Santos and Yan Levin Water and other tetrahedral liquids: order, anomalies and solvationB Shadrack Jabes, Divya Nayar, Debdas Dhabal, Valeria Molinero and Charusita Chakravarty Diffusion coefficient and shear viscosity of rigid water modelsSami Tazi, Alexandru Boţan, Mathieu Salanne, Virginie Marry, Pierre Turq and Benjamin Rotenberg Phase behaviour of colloidal assemblies on 2D corrugated substratesSamir El Shawish, Emmanuel Trizac and Jure Dobnikar Structural properties of dendrimer-colloid mixturesDominic A Lenz, Ronald Blaak and Christos N Likos Fluid-fluid demixing of off-critical colloid-polymer systems confined between parallel platesE A G Jamie, R P A Dullens and D G A L Aarts Simulations of nematic homopolymer melts using particle-based models with interactions expressed through collective variablesKostas Ch Daoulas, Victor Rühle and Kurt Kremer Smectic shellsTeresa Lopez-Leon, Alberto Fernandez-Nieves, Maurizio Nobili and Christophe Blanc Intrinsic profiles and the structure of liquid surfacesP Tarazona, E Chacón and F Bresme Competing ordered structures formed by particles with a regular tetrahedral patch decorationGünther Doppelbauer, Eva G Noya, Emanuela Bianchi and Gerhard Kahl Heterogeneous crystallization in colloids and complex plasmas: the role of binary mobilitiesH Löwen, E Allahyarov, A Ivlev and G E Morfill Isotope effects in water as investigated by neutron diffraction and path integral molecular dynamicsAnita Zeidler, Philip S Salmon, Henry E Fischer, Jörg C Neuefeind, J Mike Simonson and Thomas E Markland Confined cubic blue phases under shearO Henrich, K Stratford, D Marenduzzo, P V Coveney and M E Cates Depletion-induced biaxial nematic states of boardlike particlesS Belli, M Dijkstra and R van Roij Active Brownian motion tunable by lightIvo Buttinoni, Giovanni Volpe, Felix Kümmel, Giorgio Volpe and Clemens Bechinger Structure and stability of charged clustersMark A Miller, David A Bonhommeau, Christopher J Heard, Yuyoung Shin, Riccardo Spezia and Marie-Pierre Gaigeot Non-equilibrium relaxation and tumbling times of polymers in semidilute solutionChien-Cheng Huang, Gerhard Gompper and Roland G Winkler Thermophoresis of colloids by mesoscale simulationsDaniel Lüsebrink, Mingcheng Yang and Marisol Ripoll Computing the local pressure in molecular dynamics simulationsThomas W Lion and Rosalind J Allen Gradient-driven fluctuations in microgravityA Vailati, R Cerbino, S Mazzoni, M Giglio, C J Takacs and D S Cannell.

We have investigated the possibility of decorating, using a bottom-up strategy, patchy particles in such a way that they self-assemble in (two-dimensional) Archimedean tilings. Except for the trihexagonal tiling, we have identified conditions under which this is indeed possible. The more compact tilings, i.e., the elongated triangular and the snub square tilings (which are built up by triangles and squares only) are found to be stable up to intermediate pressure values in the vertex representation, i.e., where the tiling is decorated with particles at its vertices. The other tilings, which are built up by rather large hexagons, octagons and dodecagons, are stable over a relatively large pressure range in the centre representation where the particles occupy the centres of the polygonal units.

Over the past two decades, the dynamics of fluids under nanoscale confinement has attracted much attention. Motivation for this rapidly increasing interest is based on both practical and fundamental reasons. On the practical and rather applied side, problems in a wide range of scientific topics, such as polymer and colloidal sciences, rheology, geology, or biophysics, benefit from a profound understanding of the dynamical behaviour of confined fluids. Further, effects similar to those observed in confinement are expected in fluids whose constituents have strong size or mass asymmetry, and in biological systems where crowding and obstruction phenomena in the cytosol are responsible for clear separations of time scales for macromolecular transport in the cell. In fundamental research, on the other hand, the interest focuses on the complex interplay between confinement and structural relaxation, which is responsible for the emergence of new phenomena in the dynamics of the system: in confinement, geometric constraints associated with the pore shape are imposed to the adsorbed fluids and an additional characteristic length scale, i.e. the pore size, comes into play. For many years, the topic has been mostly experimentally driven. Indeed, a broad spectrum of systems has been investigated by sophisticated experimental techniques, while theoretical and simulation studies were rather scarce due to conceptual and computational issues. In the past few years, however, theory and simulations could largely catch up with experiments. On one side, new theories have been put forward that duly take into account the porosity, the connectivity, and the randomness of the confinement. On the other side, the ever increasing available computational power now allows investigations that were far out of reach a few years ago. Nowadays, instead of isolated state points, systematic investigations on the dynamics of confined fluids, covering a wide range of system parameters, can be realized. In fact, theory and simulations were recently able to predict new and surprising dynamical features, such as the occurrence of sub-diffusive laws, which result from the trapping due to the geometric and topological constraints and/or quenched disorder, the presence of both continuous and discontinuous glass transitions, and diffusion-localization transitions. Together, theory and simulations are thus able to contribute to a deeper insight into the complex dynamical behaviour of fluids in disordered confinement. Still, many yet unsolved problems remain. The fact that theoretical and simulation approaches have caught up with experimental investigations, has motivated us to organize a workshop on the dynamics of fluids confined in disordered environments, so as to bring together the different communities working in this field: theory and simulations, with their recent developments based on the mode-coupling theory of the glass transition, and experiments, with particular emphasis on colloidal systems and novel techniques. In an effort to give credit to recent developments in related problems of biophysical relevance, an entire session of the programme was dedicated to anomalous diffusion in crowded environments. The workshop was thus aimed at providing a deeper understanding of the complex dynamics of fluids in confinement as well as up-to-date perspectives on the interdisciplinary applications of this field of research. We are proud to say that all 32 contacted speakers accepted our invitation. Additional participants were attracted by our scientific programme, contributing poster presentations to the workshop. In total, close to 50 participants were registered, arriving from 11 different countries (including the US, Japan, and Mexico). Thus we conclude that the workshop indeed addressed a highly topical scientific field. From the scientific point of view a broad range of problems was covered, ranging from biophysics over soft matter to fermion systems. From the vivid discussions it became evident that the close scientific contact between theory, simulation and experiment brought along a fruitful and mutually inspiring atmosphere. On the theoretical side, these discussions have allowed clarification of several connections between the dynamics of models of fluids in porous media (quenched-annealed, pinned particles models), those of well-known limiting cases (Lorentz gas), of realistic models of liquids with strong dynamic asymmetry (asymmetric size and mass mixtures, sodium silicates, polymers blends) and even of bulk glass-formers. On the experimental side, it appeared that soft matter systems may provide an excellent test-bed to verify the theoretical predictions. From the concluding discussion it was also clear that addressing related issues relevant to biology still remains an open challenge for the future. In view of all this, it was concluded that within a short time period a workshop with analogous scope should be organized to address the progress made on both fundamental and interdisciplinary aspects. The realization of this workshop was made possible by generous financial support from CECAM, Centre Blaise Pascal-ENS de Lyon, and the ESF network 'Molecular Simulations in Biosystems and Material Science' (SimBioMa). Complex dynamics of fluids in disordered and crowded environments contents Phonon dispersions of cluster crystals Tim Neuhaus and Christos N Likos Challenges in determining anomalous diffusion in crowded fluids Marcel Hellmann, Joseph Klafter, Dieter W Heermann and Matthias Weiss Diffusion of active tracers in fluctuating fields David S Dean and Vincent Demery Self-diffusion of non-interacting hard spheres in particle gels Jean-Christophe Gimel and Taco Nicolai Probing glassy states in binary mixtures of soft interpenetrable colloids E Stiakakis, B M Erwin, D Vlassopoulos, M Cloitre, A Munam, M Gauthier, H Iatrou and N Hadjichristidis Fluids with quenched disorder: scaling of the free energy barrier near critical points T Fischer and R L C Vink Lennard-Jones binary mixture in disordered matrices: exploring the mode coupling scenario at increasing confinement P Gallo and M Rovere Static and dynamic contributions to anomalous chain dynamics in polymer blends Marco Bernabei, Angel J Moreno and J Colmenero Anomalous transport of a tracer on percolating clusters Markus Spanner, Felix Hofling, Gerd E Schroder-Turk, Klaus Mecke and Thomas Franosch Long-wavelength anomalies in the asymptotic behavior of mode-coupling theory S K Schnyder, F Hofling, T Franosch and Th Voigtmann Dynamic arrest of colloids in porous environments: disentangling crowding and confinement Jan Kurzidim, Daniele Coslovich and Gerhard Kahl Slow dynamics, dynamic heterogeneities, and fragility of supercooled liquids confined in random media Kang Kim, Kunimasa Miyazaki and Shinji Saito

Reference EPFL-ARTICLE-147300doi:10.1088/0953-8984/22/10/100301View record in Web of Science Record created on 2010-03-16, modified on 2016-08-08

We numerically study the condensed phases of repelling core-softened spheres confined to a planar cell at the crossover from two to three dimensions. In the related experiment presented in Osterman et al (2007 Phys. Rev. Lett.99 248301) the dipolar interaction between superparamagnetic spheres trapped in a thin cell was induced by a transverse magnetic field and tuned by adjusting the cell thickness. Depending on the cell thickness, the interaction can be purely repulsive (2D dipole‐dipole), softened repulsive, or attractive at small distances. Clustering of colloids without any attractive force has been observed. Here we analyze the observed mesophases numerically by means of Monte Carlo simulations and by genetic algorithms based energy optimization. We observe the same phases seen in the experiment including expanded hexagonal, square, chain-like, stripe/labyrinthine, and honeycomb structures.

Recently, particular interest has been placed in the study of a strikingly counter-intuitive phenomenon: the clustering of purely repulsive soft particles. This contribution serves the purpose of both reviewing our current understanding of the multiple occupancy crystals and presenting details of recently developed tailor-cut approaches to the problem. We first indicate, by use of analytically tractable examples, how such a phenomenon can arise at all. We then show that the thermodynamic formalism has to be adapted when studying such systems and present a novel computer simulation technique apt to do so. Finally, we discuss the intriguing mechanical and structural responses of such systems upon increasing the density.

The three-yearly Liquid Matter Conference is organized by the Liquids Section of the Condensed Matter Division of the European Physical Society. This series of meetings began in Lyon in 1990. The previous meeting was held in 2005 in Utrecht. The original aim of the Liquid Matter Conference was to bring together scientists working on the liquid state of matter. A closer analysis of the program booklets over the past 18 years reveals that new and highly active research fields that are closely related to liquid matter have been successfully integrated in the scope of the conference, notably the rapidly developing fields of soft matter and biophysics. Concomitantly, a broadening of the spectrum from the classical liquid state to a wide spectrum of phases and systems could be observed. Therefore, the rapidly growing field covered by this conference series at present includes physics, chemistry, biology, and chemical engineering as well as various applied research areas. Liquid state physics is at the interface of many research fields. As a consequence, many of the attendants come from adjacent fields and encounter at the Liquid Matter Conference a community where they can meet experts from other research areas. This aspect of the Liquid Matter Conference makes it an exciting meeting as it not only offers the participants an up-to-date picture of the status of research into the liquid state of matter, but it also allows them to establish new (and often unexpected) transdisciplinary contacts for joint scientific endeavours. This applies in particular to the area of soft condensed matter such as colloidal suspensions, polymeric systems and biological materials. The Lund meeting, organized in collaboration with Lund University, had 574 registered participants from five continents. During the conference, and following the tradition established at the Utrecht meeting, the second Liquid Matter Prize of the European Physical Society was awarded to Professor Henk Lekkerkerker (Utrecht) and to Professor Peter Pusey (Edinburgh) for their seminal studies of colloidal matter. In addition to plenary speeches by the two recipients of the Liquid Matter Prize, the scientific program consisted of ten plenary lectures, 108 symposia talks, 23 of which were keynote lectures, and 458 poster contributions. This special issue of Journal of Physics: Condensed Matter contains 47 of the oral communications. The conference was held in the buildings of Lund University and the Student Union facing the University Square in the heart of Lund. The organizers gratefully acknowledge the substantial financial support offered by the Nobel Foundation and by the Swedish Research Council. The success of the conference owes a great debt of gratitude to the members of the Local Organizing Committee and all the people who helped them tirelessly (and very efficiently) to make the conference run smoothly and to the members of the International Program Committee, who were deeply involved in the planning of the conference. During the conference dinner our colleague Lennart Piculell gave a singing performance, which included a song dedicated to the two winners of the Liquid Matter Prize, entitled Hard-Breaking Gel, whose lyrics are printed below. Finally, the Board of the Liquids Section of the European Physical Society decided that the 8th Liquid Matter Conference will be held in Vienna (Austria) 6–10 September 2011. Hard-Breaking Gel New lyrics by Lennart Piculell to the melody of Heartbreak Hotel, created in June 2008 for the 7th Liquid Matter Conference, dedicated to Henk Lekkerkerker and Peter Pusey. Well, since my baby left me, I found a new place to be! It's downtown Lund, in a narrow street, Where hundreds of cool people meet! There I don't feel lonely, No, I don't feel lonely - So, if you feel lonely, you should try! It's all about liquid matter: Liquids flow, and soft bodies swell! Your mind is blown, and your blood will boil To a hard-breaking gel. And you won't be lonely, No, you won't be lonely - So, if you feel lonely, you should try! A tough guy tells you: Freeze! This is something that you have to test, 'Cause when you freeze you'll be super-cool, Or else you'll be under arrest. But you won't be lonely, baby, No, you won't be lonely, baby - So, if you feel lonely, you should try! I learn that the slightest nano-rod, That wouldn't seem very large; It still can fill up a lot of space As soon as you give it some charge! So, if you feel lonely, baby, Yes, if you feel lonely, baby - If you feel lonely, you should try! Well, when the party's over, What memories will time erase? Well, the chemistry may be lost on me, But I never forget a phase! And I won't be lonely, No, I won't be lonely - I won't be lonely 'til I die!

Introducing genetic algorithms as a reliable and efficient tool to find ordered equilibrium structures, we predict minimum energy configurations of the square shoulder system for different values of corona width $\lambda$. Varying systematically the pressure for different values of $\lambda$ we obtain complete sequences of minimum energy configurations which provide a deeper understanding of the system's strategies to arrange particles in an energetically optimized fashion, leading to the competing self-assembly scenarios of cluster-formation vs. lane-formation., Comment: 5 pages, 6 figures

The authors discuss the application of the new thermodynamically self-consistent integral equations for the determination of the structural properties of liquid metals. They present a detailed comparison of the structure (S(q) and g(r)) for models of liquid alkali metals as obtained from two thermodynamically self-consistent integral equations and some published exact computer simulation results; the range of states extends from the triple point to the expanded metal. The theories which only impose thermodynamic self-consistency without any fitting of external data show an excellent agreement with the simulation results, thus demonstrating that this new type of integral equation is definitely superior to the conventional ones (hypernetted chain, Percus-Yevick, mean spherical approximation, etc.).

We present a first application of the very reliable modified hypernetted-chain (MHNC) integral equation for liquid metals to the analysis of a very recent experimental study on the structure of liquid potassium as a function of temperature by Jal et al. The theoretical model is based on a simple Ashcroft empty-core pseudopotential with the Ichimaru-Utsumi dielectric function. The value chosen for the core radius (1.225 A) gives good overall agreement between the calculated structure factors and the experimental ones over a wide range of temperatures. We then show how this method can be applied to investigate the qualities of the given interatomic potential by analysing at the same time and consistently thermodynamics, structural and transport properties of the liquid.

It is by now well established that the structures of the elements in the liquid state follow characteristic trends reminiscent of the trends among the crystal structures of the elements. The crystal structures have been discussed very recently by Hafner and Heine (1983) in terms of the systematic variations of the effective interatomic pair potentials with electron density and pseudopotential. The present analysis of the liquid structures is based on the same set of interatomic potentials and on the optimised random-phase approximation (ORPA) for the calculation of the liquid structure. The authors show that the structural trends in the liquid and crystalline states have the same physical origin. The complex structures of the light polyvalent liquid metals (Ga, Si, Ge) are shown to arise from the interplay of two characteristic distances: the effective diameter of the hard repulsive core expressing the geometrical requirements of sphere packing and the Friedel wavelength of the oscillatory part of the potentials characterising the electronic effects in the metallic bonding. The return to hard-sphere-like structures for the heavy elements stems from the disappearance of the leading term of the Friedel oscillations as the core radius Rc approaches a value for which 2kFRc=1/2 pi .

The authors present an extension of the blip-function expansion of Weeks, Chandler and Andersen (WCA) (1971) to liquid binary alloys. It turns out that the fact that realistic interionic pair potentials tend to be non-additive for most alloys poses a serious problem. They propose to resolve this problem by modifying the separation of the pair potentials in repulsive short-range and long-range terms in such a way that the repulsive parts are always additive, the non-additivity being entirely absorbed in the long-range terms. They show that this results in a first important improvement of the structure of liquid alloys over a simple hard-sphere picture. However, we emphasise that this should only be considered as a first step towards a systematic application of thermodynamic perturbation theory to liquid alloys.

The density functional theory of freezing is applied to the calculation of the liquid-solid phase diagram of Al and Mg. The calculation predicts the freezing into the correct crystal structure, FCC for Al and HCP for Mg. At normal pressures, it is predicted that freezing into hypothetical HCP Al will occur at a temperature 360 K below the freezing point of FCC Al, and that the solidification temperature of FCC Mg is depressed by 190 K compared with HCP Mg. Both values are in good agreement with thermochemical estimates.