Effect of vacancies on the structure of solid molecular parahydrogen studied with variational Monte Carlo simulations

We performed variational Monte Carlo simulations with a shadow wave function to study the effects of vacancies on the structure of solid molecular p-H-2. In a quantum crystal, vacancies tend to modify the local order in the crystal. The main mechanism is due to the fact that molecules tend to occupy the empty space in order to lower the kinetic energy. While this effect is expected to be more important at lower than at higher densities, we find that in the latter case the local order is even more affected by the presence of a vacancy. Results on the occurrence of quantum diffusion of the vacancy in the solid are also presented.