Structural and thermodynamic properties of diamond: A path-integral Monte Carlo study

Path-integral Monte Carlo simulations in the isothermal-isobaric ensemble have been carried out to study structural and thermodynamic properties of diamond, as a function of temperature and hydrostatic pressure. Atomic nuclei were treated as quantum particles interacting through a Tersoff-type potential. The obtained lattice parameter, heat capacity, thermal expansion coefficient, and bulk modulus show an overall agreement with the experimental data. The importance of anharmonicity and quantum effects on the properties derived from the quantum simulations has been assessed by comparison with results obtained in classical simulations with the same interatomic potential, as well as with those derived from a quasiharmonic approximation. An increase in the lattice parameter by 1.7×10^-2 {} and a decrease in the bulk modulus by about $5%$ is found at low temperatures, as a consequence of the zero-point motion of the C atoms.