Simulation of phase equilibria from first principles: Basis set and density functional dependence

The simulation package CP2K has been extended to include advanced Monte Carlo algorithms. These routines, along with the mixed basis set Quickstep routine for computing the forces and energies of systems described by density functional theory, have been used to explore the phase equilibria of water for different density functionals, plane wave cutoffs, and basis sets. The initial Monte Carlo routines were validated against first principles molecular dynamics simulations (CP2K and CPMD) for which comparable ensembles could be used. Methods to improve efficiency (such as pre-biasing moves with less expensive potentials) have also been implemented and their efficacy is examined.