First Principles Monte Carlo Simulations of Elemental Fluid Phase Equilibria

We use modern Monte Carlo sampling methods in concert with standard electronic structure codes (primarily NWChem) to perform liquid-vapor and liquid-liquid coexistence calculations from first principles.  In order to improve computational efficiency an approximate "pre-sampling" potential is used to generate large moves with a high probability of acceptance.  A hybrid approach in which two "levels" of pre-sampling is constructed, in which the first uses an empirical potential, and the second uses density functional theory but with a very low (and fixed) number of plane waves.

Issues of efficiency, correctness and load-balancing arising from the use of iterative density functional theory potentials are addressed
both directly and through analysis of model systems.  System size effects are also tested using model systems.  Results are presented
from Gibbs- ensemble calculations on group I and group II metals and mixtures. Extensions of these calculations to determination of elemental solubilities in molten metals are also presented.