Evaluation of Tersoff's Revised Silicon Potential in a Molecular Dynamic Simulation of Solid Silicon.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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The goal of this research was to provide an initial testing of a new silicon potential proposed by Tersoff. Molecular Dynamic MD simulations were performed at four temperatures below the melting point of silicon to evaluate the new potentials ability to reproduce the characteristics of diamond-Si. A constant enthalpy ensemble composed of 64 atoms was used for the evaluation. Although the Tersoff potential does identify the diamond structure as the lowest energy crystal at absolute zero, problems were noted at higher temperatures. At all temperatures above zero, the calculational cell showed a marked decrease in volume. The amount of system shrinkage increased with increasing simulation temperature. Because of this shrinkage, the Tersoff potential is unusable in MD simulations. Several attempts were made to isolate and identify the cause of the shrinkage, but were unsuccessful. It was noted that as the bonding environment became more favorable stronger bonding, the bonding radius of minimum energy decreased. Since the potential relies primarily on coordination number to stabilize the diamond structure, it is postulated that there exists an as-yet unidentified four-bond configuration that provides a lower energy and as a result has a shorter rest bond length than the tetrahedral diamond structure.
- Nuclear Physics and Elementary Particle Physics