Quantum atomistic simulations of silicon and germanium

Quantum atomistic simulations of crystalline silicon and germanium have been carried out by the path-integral Monte Carlo method. The interatomic interactions were modeled by Stillinger-Weber-type potentials, with parameters adequate to quantum simulations. Quantum zero-point motion together with anharmonicity of the interatomic potential led to a lattice expansion of 7 x 10(-3) Angstrom for both Si and Ge. Results for the equation-of-state (volume versus pressure) and for the thermal expansion coefficient agreed well with experimental results for both materials at T>100 K and for hydrostatic pressures up to 100 kbar.