Thermodynamic properties of<i>c</i>-Si derived by quantum path-integral Monte Carlo simulations

Abstract

Feynman path-integral Monte Carlo simulations of crystalline silicon, using the empirical potential of Stillinger and Weber, have been performed in the isothermal-isobaric ensemble. Several thermodynamic properties have been evaluated as a function of pressure and temperature. The calculated lattice parameter, heat capacity, thermal expansion coefficient, and bulk modulus show an overall agreement with the experimental data. However, the negative thermal expansion of silicon at temperatures below 120 K is not reproduced with this model potential. The importance of anharmonicity and quantum effects on the properties derived from the Stillinger-Weber potential is addressed by comparison with the results expected in a quasiharmonic approximation and in the classical limit. \textcopyright{} 1996 The American Physical Society.