http://www.bibsonomy.org/burst/user/statphys23/freeBibSonomy BuRST Feed for /user/statphys23/free2008-10-08T13:12:54+02:00http://www.bibsonomy.org/bibtex/2bfe7974fc23938723de31ed6b010a8dd/statphys23statphys232007-06-20T10:16:09+02:00ising energy model calculations topic-3 thermodynamics nonequilibrium free statphys23 <span style="color:#555555;">G. <a href="http://www.bibsonomy.org/author/Sutmann">Sutmann</a> und H. <a href="http://www.bibsonomy.org/author/Hijar">Hijar</a> und J. <a href="http://www.bibsonomy.org/author/Quintana">Quintana</a> </span><em>Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, </em><em>Genova, Italy, </em><em>9-13 July2007. </em>Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulyFree Energy Differences for the 2D-Ising Model from Non-Equilibrium Work Theorems2007ising energy model calculations topic-3 thermodynamics nonequilibrium free statphys23 The two-dimensional Ising model is studied under the influence of an external magnetic field by means of Monte Carlo simulations. Of special interest is the work which is performed when the field is switched on or off. Traditionally this work is calculated by means of thermodynamic integration which requires a large number of simulation steps in order to move the system from the initial to the final state through equilibrium states. In the present work, non-equilibrium simulations are performed, where the field is switched on or off in a small number of steps. Additionally the system is allowed to relax for one Monte Carlo step between two successive magnetic field strengths. By measuring the work performed in each non-equilibrium experiment, a distribution function for the work is obtained. Calculations were carried out below and above, as well as close to the critical temperature $T_c$. In addition, different rates for the switching process of the magnetic field were studied. In order to calculate free energy differences in the system, the work distribution functions were used to apply the Jarzynski and Crooks fluctuation theorems. Both were verified by comparing results to those from thermodynamic integration. It is found that free energy differences agree very well within error bars. However, it is found that the Crooks fluctuation theorem provides a significantly faster method for the evaluation of free energy differences in the system with respect to the Jarzynski equality. As expected, for temperatures far from $T_c$ the convergence of the results is faster than for $T\approx T_c$, where a slower switching rate is needed.http://www.bibsonomy.org/bibtex/2088a90dfa4582b8b6b5c4fdd9ae9e81e/statphys23statphys232007-06-20T10:16:09+02:00statphys23 orientational biological membrane topic-10 intrinsic budding shape ordering free energy <span style="color:#555555;">A. <a href="http://www.bibsonomy.org/author/Iglic">Iglic</a> und J. <a href="http://www.bibsonomy.org/author/Urbanija">Urbanija</a> und H. <a href="http://www.bibsonomy.org/author/Hagerstrand">Hagerstrand</a> und V. <a href="http://www.bibsonomy.org/author/Kralj Iglic">Kralj Iglic</a> </span><em>Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, </em><em>Genova, Italy, </em><em>9-13 July2007. </em>Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulyOn the role of anisotropy of membrane constituents in budding of biological membranes2007statphys23 orientational biological membrane topic-10 intrinsic budding shape ordering free energy The budding of biological membrane is studied theoretically and experimentally. The theoretical description starts from a single-constituent energy that reflects intrinsic shape of the constituents, and uses methods of statistical physics to obtain membrane free energy. The membrane free energy is minimized to yield the equilibrium shape of the membrane and lateral and orientational distribution functions of membrane constituents in the budding region. It is shown that two mechanisms based on internal degrees of freedom: in-plane orientational ordering of membrane constituents and non-homogeneous lateral distribution of membrane constituents, are complementary mechanisms that promote budding of the membrane. References: 1. V. Kralj-Iglic, B. Babnik, D.R. Gauger, S. May, A. Iglic, Quadrupolar ordering of phospholipid molecules in narrow necks of phospholipid vesicles, J. Stat. Phys. 125 (2006) 727-752. 2. H. Hagerstrand, L. Mrowczynska, U. Salzer, R. Prohaska, K.A Michelsen, V. Kralj-Iglic, A. Iglic, Curvature dependent lateral distribution of raft markers in the human erythrocyte membrane. Mol. Membr. Biol. 23 (2006) 277-288.http://www.bibsonomy.org/bibtex/2844272e14432d781e60bfcbc0aec471e/statphys23statphys232007-06-20T10:16:09+02:00single statphys23 recovery theorems fluctuation energy metastable free molecule experiments misfolding topic-1 states <span style="color:#555555;">I. <a href="http://www.bibsonomy.org/author/Junier">Junier</a> und F. <a href="http://www.bibsonomy.org/author/Ritort">Ritort</a> </span><em>Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, </em><em>Genova, Italy, </em><em>9-13 July2007. </em>Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulyFree energy recovery of metastable states from a generalized fluctuation theorem2007single statphys23 recovery theorems fluctuation energy metastable free molecule experiments misfolding topic-1 states Fluctuation theorems allow to recover free energy differences between equilibrium states corresponding to different values of an external control parameter. I will present a generalized fluctuation theorem that allows to recover free energies of metastable states from experimental measurements of the irreversible work. The new relation is applied to measure the free energy of metastable unfolded states and misfolded states observed in single molecule force experiments in RNA folding.http://www.bibsonomy.org/bibtex/246a02490ae12df8a20e0476721ea4c85/statphys23statphys232007-06-20T10:16:09+02:00topic-7 standing free crystals interaction transitions liquid films smectic-a phase fluctuation-induced statphys23 <span style="color:#555555;">I.N. <a href="http://www.bibsonomy.org/author/De Oliveira">De Oliveira</a> und M.L. <a href="http://www.bibsonomy.org/author/Lyra">Lyra</a> und L.V. <a href="http://www.bibsonomy.org/author/Mirantsev">Mirantsev</a> </span><em>Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, </em><em>Genova, Italy, </em><em>9-13 July2007. </em>Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulyCasimir-like force in free-standing smectic films close to Smectic A – Nematic phse transition2007topic-7 standing free crystals interaction transitions liquid films smectic-a phase fluctuation-induced statphys23 It is well known that a thermal Casimir-like force emerges in highly correlated classical systems due to thermal fluctuations. It is particularly important in liquid crystal where the long range character of this interaction has been shown to be relevant to several interesting phenomena, such as wetting and unbinding of fluid membranes. Free-standing smectic films are formed by a stack of smectic ayers confined by a surrounding gas. The effective coupling between the film and the gas is mimicked by a surface tension term which reduces surface fluctuations of the smectic order and provides the characteristic quasi-long range order with logarithmically diverging fluctuations. As a result, the fluctuation-induced interactions decay as $1/l^2$, where $l$ is the film thickness. This effective interaction between surfaces of free-standing films has a longer range than the usual van der Walls interaction. In this work, the thermal Casimir-like in free-standing liquid crystal films close to smectic-A – nemactic transition temperature is computed using a quadratic functional integral approach. In the framework of a microscopic mean-field model of free-standing films, the temperature dependence of the order parameter profiles is computed and later used estimated the elastic coupling variability in the vicinity of first- and second order bulk smectic-A – nematic phase transitions. The strong nonuniformity of the coupling constant profiles promotes a significant increase of the fluctuation-induced force over three orders of magnitude, specially in thin films. This results reinforces the possible predominance of the thermal Casimir force as compared to the standard van der Waals interaction in thin smectic-A liquid crystal films.http://www.bibsonomy.org/bibtex/2862e09b2c037c40453b6fcb15a43ea82/statphys23statphys232007-06-20T10:16:09+02:00energies interface wetting surface statphys23 partial alkali topic-6 halides nomelting nanofriction free <span style="color:#555555;">T. <a href="http://www.bibsonomy.org/author/Zykova Timan">Zykova Timan</a> und D. <a href="http://www.bibsonomy.org/author/Ceresoli">Ceresoli</a> und U. <a href="http://www.bibsonomy.org/author/Tartaglino">Tartaglino</a> und E. <a href="http://www.bibsonomy.org/author/Tosatti">Tosatti</a> </span><em>Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, </em><em>Genova, Italy, </em><em>9-13 July2007. </em>Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulyPhysics and Nanofriction of NaCl Surfaces near the Melting Point2007energies interface wetting surface statphys23 partial alkali topic-6 halides nomelting nanofriction free The high temperature surface properties of alkali halides are very unusual, as the crystal surfaces are incompletely wetted by their own melt. Classical molecular dynamics simulations based on the Tosi-Fumi potential provide a unique opportunity, where all surface properties of this model system can be calculated and intimately understood. We found that crystalline NaCl(100) is nonmelting, and remains in this model stable and free of precursor signals of melting up to the bulk melting point $T_m$, where a simulated droplet of melt indeed shows partial wetting. Building on simulations, we calculated the solid-vapor, liquid-vapor, and solid-liquid interface free energies as a function of temperature. Analysis of these results shows that the anomalous wetting properties of NaCl(100) eventually stem from three reasons: (i) the solid surface is enormously anharmonic, with a very low free energy; (ii) the solid-liquid interface is instead relatively costly, on account of a very large density difference; (iii) the liquid surface free energy is finally surprisingly high, despite an apparent lack of local crystal-like order. Calculations reveal a liquid surface entropy deficit, whose reason is traced to short range incipient molecular order.[1] Its extreme nonwetting properties may make crystalline NaCl(100) an ideal substrate for studies of high temperature sliding nanofriction by hard tips. We conducted direct nanofriction simulations both in the heavy ploughing, wear-dominated regime, and in the light grazing, wearless friction regime. Plowing friction is found to drop close to melting (as in ice skating). Grazing friction peaks instead close to melting, where linear response shows the solid surface compliance to surge.[2] References\\ 1) T. Zykova-Timan, D. Ceresoli, U. Tartaglino, E. Tosatti, Phys. Rev.Lett. 94, 176105 (2005); J. Chem. Phys. 123, 164701 (2005).\\ 2) T. Zykova-Timan, D. Ceresoli, E. Tosatti, Nature Materials 6, 231 (2007).http://www.bibsonomy.org/bibtex/254c8e295266c227488d61c054ec7922b/statphys23statphys232007-06-20T10:16:09+02:00energy statphys23 free glass transition landscape topic-9 <span style="color:#555555;">T. <a href="http://www.bibsonomy.org/author/Ekimoto">Ekimoto</a> und A. <a href="http://www.bibsonomy.org/author/Yoshimori">Yoshimori</a> und T. <a href="http://www.bibsonomy.org/author/Odagaki">Odagaki</a> </span><em>Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, </em><em>Genova, Italy, </em><em>9-13 July2007. </em>Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulyRelaxation processes in the Free Energy Landscape2007energy statphys23 free glass transition landscape topic-9 We present a phenomenological understanding of three relaxation processes; fast, slow and Johari-Goldstein(JG) in glass forming substances on the basis of the Free Energy Landscape(FEL). The representative point in the FEL is assumed to obey the time dependent Ginzburg-Landau(TDGL) type equation with the FEL as the driving force. We analyze the generalized susceptibility for a toy model of the FEL. We demonstrate that fast and slow relaxations are determined by the oscillatory motion within a basin and the jump motion among basins, respectively and that the relaxation time of these relaxations is determined by the curvature of the FEL around a local minimum and the depth of the FEL, respectively. We also demonstrate that JG relaxation is determined by the minor modulations of the FEL which is produced by the internal degree of freedom of constituents.http://www.bibsonomy.org/bibtex/20cef11157d969d9053f7bb5f641036ec/statphys23statphys232007-06-20T10:16:09+02:00topic-6 theory sodium interfacial statphys23 energy free chloride classical nucleation <span style="color:#555555;">T. <a href="http://www.bibsonomy.org/author/Zykova">Zykova</a> und C. <a href="http://www.bibsonomy.org/author/Valeriani">Valeriani</a> und E. <a href="http://www.bibsonomy.org/author/Sanz">Sanz</a> und D. <a href="http://www.bibsonomy.org/author/Frenkel">Frenkel</a> und E. <a href="http://www.bibsonomy.org/author/Tosatti">Tosatti</a> </span><em>Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, </em><em>Genova, Italy, </em><em>9-13 July2007. </em>Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulyClassical Nucleation Theory cannot be used to determine solid-liquid interface free energies of crystals2007topic-6 theory sodium interfacial statphys23 energy free chloride classical nucleation We compare the values of the solid-liquid interface free energy of NaCl crystals as obtained from simulations of the crystal nucleation barrier with those obtained from numerical studies of the solid-liquid contact-angle near the triple point. We find that the values obtained by these different methods differ by more than a factor two. We analyse the possible sources for this discrepancy and conclude that, within the framework of Classical Nucleation Theory, experiments on crystal nucleation alone provide insufficient information to yield reasonable estimates for the solid-liquid surface free energy.http://www.bibsonomy.org/bibtex/2668ed7f3bc3bbcad7a1999709dc5036f/statphys23statphys232007-06-20T10:16:09+02:00energy metastable relaxation free widom statphys23 liquids topic-6 line network-forming liquid barrier <span style="color:#555555;">G. <a href="http://www.bibsonomy.org/author/Franzese">Franzese</a> und P. <a href="http://www.bibsonomy.org/author/Kumar">Kumar</a> und H.E. <a href="http://www.bibsonomy.org/author/Stanley">Stanley</a> </span><em>Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, </em><em>Genova, Italy, </em><em>9-13 July2007. </em>Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulyDynamic crossover at the Widom temperature in metastable liquid water and other network-forming liquids.2007energy metastable relaxation free widom statphys23 liquids topic-6 line network-forming liquid barrier On decreasing the temperature $T$, experiments on supercooled water and other network-forming liquids, such as BeF$_2$ or SiO$_2$, display a dynamic crossover from non-Arrhenius dynamics (with $T$-dependent activation energy) to Arrhenius dynamics (with constant activation energy). We show, by computer simulations and analytic results, that this dynamic behavior is related to the anomalous increase of fluctuations at low $T$. We locate the temperature of maximum fluctuation $T_W$ along the Widom line, which is expected to depart from a metastable liquid-liquid critical point. We find that $T_W$ corresponds to the maximum structural change in the liquid. We recover the dynamic crossover directly from the calculation of the free energy associated with breaking a bond and reorienting the molecule, showing that the dynamics is Arrhenius at low $T$ because of the structural change occurring at $T_W$. By analyzing the pressure-dependence of the crossover, it is possible to give insight into the mechanism ruling the physics of network-forming liquids.http://www.bibsonomy.org/bibtex/2b4ed257693305a4abca485afdc11a9a1/statphys23statphys232007-06-20T10:16:09+02:00topic-11 scale statphys23 fitness networks free complex model <span style="color:#555555;">C. <a href="http://www.bibsonomy.org/author/Bedogne Rodgers">Bedogne Rodgers</a> </span><em>Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, </em><em>Genova, Italy, </em><em>9-13 July2007. </em>Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulyComplex growing networks with intrinsic vertex fitness2007topic-11 scale statphys23 fitness networks free complex model One of the major questions in complex network research is to identify the range of mechanisms by which a complex network can self organize into a scale-free state. In this paper we investigate the interplay between a fitness linking mechanism and both random and preferential attachment. In our models, each vertex is assigned a fitness x, drawn from a probability distribution (x). In Model A, at each time step a vertex is added and joined to an existing vertex, selected at random, with probability p and an edge is introduced between vertices with fitnesses x and y, with a rate f(x,y), with probability 1–p. Model B differs from Model A in that, with probability p, edges are added with preferential attachment rather than randomly. The analysis of Model A shows that, for every fixed fitness x, the network's degree distribution decays exponentially. In Model B we recover instead a power-law degree distribution whose exponent depends only on p, and we show how this result can be generalized. The properties of a number of particular networks are examined.http://www.bibsonomy.org/bibtex/2d35aa4fb093584da79540f607a23f7e1/statphys23statphys232007-06-20T10:16:09+02:00bio-molecules geometry fluid topic-10 statphys23 energy hard-sphere free integral solvation <span style="color:#555555;">H. <a href="http://www.bibsonomy.org/author/Hansen Goos">Hansen Goos</a> und R. <a href="http://www.bibsonomy.org/author/Roth">Roth</a> und K. <a href="http://www.bibsonomy.org/author/Mecke">Mecke</a> und S. <a href="http://www.bibsonomy.org/author/Dietrich">Dietrich</a> </span><em>Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, </em><em>Genova, Italy, </em><em>9-13 July2007. </em>Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulySolvation free energies of bio-molecules from a geometry-based approach2007bio-molecules geometry fluid topic-10 statphys23 energy hard-sphere free integral solvation Inspired by Hadwiger's theorem from integral geometry we develop a method for the calculation of solvation free energies of bio-molecules in various types of solvent. Special attention is paid to effects due to solvent {\em entropy} which we investigate by using recent accurate density functional theory (DFT) results for the hard-sphere fluid [1]. When chain-like molecules are considered, we find regimes where, depending on the state of the solvent, either a tightly packed helical or a $\beta$-sheet structure is favored. The approach is extended to more realistic solvents which exhibit intermolecular attraction and experience specific interactions with the solute molecule, allowing for studying the effect of hydrophobicity and hydrophilicity. The high computational efficiency of our method allows us to scan a large range of solvent as well as solute configurations. We confirm the accuracy of the method by comparison with full DFT calculations for fluids under confinement. 1) H. Hansen-Goos and R. Roth, J. Phys.: Condens. Matter {\bf 18}, 8413 (2006).