Computer Simulations of Phase Transitions

University Of Georgia Research Foundation Inc, Athens GA

Investigators

Abstract

TECHNICAL SUMMARY: This award supports theoretical research and education in the use of state-of-the-art computer simulations. The research complements traditional theoretical and experimental approaches in the study of challenging problems in statistical physics that involve phase transitions. The program of research is diverse in scope, broadly developing methods to study phase transitions in systems that cannot be treated analytically. The methods used include Monte Carlo and Spin Dynamics simulations and these employ sophisticated software packages are being enhanced by the research group. This is part of a significant effort in the ongoing exploration and development and refinement of new large-scale simulation methods. A diverse set of physical systems are examined with particularly attention to those with relevance to magnetic materials, growing films, polymers, and proteins. Both static and dynamic critical phenomena for systems in equilibrium are examined, and this includes simple non-equilibrium models related to film growth and superionic diffusion (driven diffusive systems). Monte Carlo simulations are used to explore models with coupled magnetic and elastic degrees of freedom, lattice systems with geometric frustration (a physical system with intrinsic local frustration between magnetic spins on a pyrochlore lattice) or competing interactions, and systems with finite geometries and associated boundaries. The resulting behavior, which is fundamentally different than that which is found in the bulk, is a primary motivator of the research. Spin dynamics simulations are also used to explore dynamic phenomena for systems in equilibrium. Nonequilibrium behavior is examined in models related to film growth and superionic diffusion is studied using Monte Carlo and Kinetic Monte Carlo methods. The results are compared with those from theory and experiment. The combination of the discovery and explanation of the phase transition behavior and possible new universality classes together with the anticipated methodological developments forms a coherent activity with substantive intellectual substance. The effort undertaken has broader impacts with both scientific and educational consequences. There are many analogous phenomena in other fields, and the understanding of those systems will also be enhanced. For example, the problem of protein folding has much in common, e.g. a rough ?energy landscape?, with magnetic models with frustration. Many of the algorithmic implementations and advances have applicability to a wide range of simulations in different areas. In many sub-areas of investigation (including chemistry, biochemistry, and statistics) the improvements in Wang-Landau sampling are broadly applicable. The research provides training of graduate students in a broad range of computer simulation methods and enables them to pursue scientific careers in multiple related fields. The Center for Simulational Physics where this work is carried out has an excellent record of educating graduate students from other institutions as well as those from The University of Georgia. The annual Workshop hosted by the Center continues to provide a forum for exchange of ideas and information. NONTECHNICAL SUMMARY: This award supports research and education in the use of state-of-the-art computer simulations. The research complements traditional theoretical and experimental approaches in the study of challenging problems in statistical physics that involve phase transitions. The program of research is diverse in scope, broadly developing methods to study phase transitions in systems that cannot be treated analytically. The methods employ sophisticated software packages are being enhanced by the research group. This is part of a significant effort in the ongoing exploration and development and refinement of new large-scale computer simulation methods. A diverse set of physical systems are examined with particularly attention to those with relevance to magnetic materials, growing films, polymers, and proteins. Both static and dynamic phenomena for systems in equilibrium are examined, and this includes simple non-equilibrium models related to film growth and driven diffusive systems. Computer simulations are used to explore models of systems with finite geometries and associated boundaries. The resulting behavior, which is fundamentally different than that which is found in the bulk, is a primary motivator of the research. The results are compared with those from theory and experiment. The combination of the discovery and explanation of the phase transition behavior and possible new phase transitions together with the anticipated methodological developments forms a coherent activity with substantive intellectual substance. The effort undertaken has broader impacts with both scientific and educational consequences. There are many analogous phenomena in other fields, and the understanding of those systems will also be enhanced. For example, the problem of protein folding has much in common with magnetic models studied. Many of the advances in computer simulation methods have applicability to a wide range of simulations in different areas. In many sub-areas of investigation (including chemistry, biochemistry, and statistics) the improvements are certainly applicable. The research provides training of graduate students in a broad range of computer simulation methods and enables them to pursue scientific careers in multiple related fields. The Center for Simulational Physics where this work is carried out has an excellent record of educating graduate students from other institutions as well as those from The University of Georgia. The annual Workshop hosted by the Center continues to provide a forum for exchange of ideas and information.