Computer Simulation Studies in Condensed Matter Physics: An Introduction

Computer simulation studies in condensed matter physics now play a fundamental role in many areas of investigation. The “status report” which is contained in this volume is the result of presentations and discussion that occurred during the 19th Annual Workshop at the Center for Simulational Physics. The texts of both longer, invited presentations as well as a number of contributed papers are included. The reader will find that the scope of sim-ulational/computational studies is broad and that substantial potential for cross-fertilization of methods between different sub-fields is evident.

The volume opens with four papers on materials properties.First,Fichthorn and Miron address the challenges associated with simulating rare events, where many time scales may be relevant. They use the hyperdynamics approach to accelerate dynamical simulation of such systems in a manner that correctly samples the equilibrium state of the fast processes while evolving the trajectories at a time scale relevant for the slow processes. This is achieved by on-the-fly consolidation of broad basins of high-frequency localized states into coarser states that incorporate the equilibrium properties of the smoothed-away minima. The authors demonstrate the technique on a realistic model system of the diffusion of Co clusters on the Cu (001) surface. Dennis and Liebig study the intensity dependence of the reflectance of three types of dielectric interference filters. They simulate the reflectance of both low- and high-intensity pulses using the finite-difference time-domain method and incorporating nonlinear optical behaviors in the field equations. The three systems are compared to assess the robustness of their reflective properties against nonlinear effects at extremely high intensities. Abraham extends his earlier work on crack instability in brittle fracture by applying a recently discovered scaling law to a model solid with a crack constrained to unidirectional travel. He finds that suppression of crack instabilities leads to constant steady-state crack speeds equivalent to crack speeds in a linear solid with elastic modulus equal to the effective elastic modulus of his model solid. To conclude this Part, Thompson and Lewis use density functional theory to conduct a detailed study of the surface structure of TiO₂ (110), making contact with a recent high-precision experiment. They find that bond angles converge relatively slowly with respect to model approximations, whereas bond lengths converge rapidly. Their results suggest changing the way surface structures for covalently bonded solids are reported, emphasizing bond lengths and angles, and not absolute positions.