QUANTUM CORRECTIONS TO THE SIMULATED PROPERTIES OF SOLIDS

It is shown that a practical procedure for including both anharmonic and quantum effects in the calculation of the properties of solids is to combine classical molecular-dynamics simulations with quantum corrections obtained with the quasiharmonic approximation. The procedure is simple to implement and possesses an ordered set of anharmonic quantum corrections. It is tested by calculations on a Lennard-Jones model for solid Ar with nearest-neighbor interactions. The results obtained are competitive with the predictions of effective-potential Monte Carlo (EPMC) and are in very good agreement with path-integral Monte Carlo results, which were obtained with a constant-pressure algorithm that includes higher-order corrections to the Trotter expansion. The lowest-order perturbative correction to EPMC is shown to be the same as the cubic part of the anharmonic quantum correction.