Classical effective particle model and its applications for fcc metals.

摘要

In this thesis, we develop a classical effective particle (CEP) model for fcc metals based on the bonding descriptions of ab initio GVB calculations on metal clusters. In this empirical classical force field model, the classical effective particles are introduced to treat explicitly the electronic degrees of freedom in fcc metals. This CEP Model has proved to be an effective classical representation of the localized interstitial electrons in fcc metals. It provides a new alternative of wide applicability for large scale simulations of the metallic systems.;The general forms of the classical potentials are set such that they represent microscopic many-body interactions in a classical manner. To fit the parameters in the force field, we employ lattice dynamics experimental information of lattice vibrations as the most reliable fitting database. The excellent fits to the experimental elastic constants and the phonon data of the fcc metals have been obtained by the CEP model. The most appealing feature of the CEP model is that the Cauchy discrepancies for the fcc metals are described correctly despite of the pair-wise nature of the CEP force field.;In order to explore the range of applicability, we apply the CEP model to situations where the geometries of the system are substantially different from the ground-state equilibriums such as the anharmonic vibrations of bulk crystals at high temperatures, defects, and surfaces. In this thesis, we present the results of the two major applications: (1) The thermodynamical properties of Cu bulk. The temperature dependent behavior of the fcc metals are studied through molecular dynamics simulations at finite temperatures. The calculated linear expansion coefficients at various temperatures demonstrate that the anharmonic behavior of the system is described correctly by the CEP model. In order to simulate a correct dynamics of the system, we adopt a special technique to handle the motions of massless particles. (2) Surface properties of Cu. First, we justify and demonstrate the utility of applying the CEP force field to systems with broken symmetry. The second goal is to demonstrate the viability of the CEP model as a consistent scheme for the study of surface dynamics. We calculate the surface-phonon spectra for three low-index Cu surfaces: the (100), the (110), and the (111) faces. (Abstract shortened by UMI.).