Implementation of ultrasoft pseudopotentials in ab initio molecular dynamics

A scheme for the construction of ultrasoft separable pseudopotentials recently proposed by Vanderbilt is tested in the context of Car-Parrinello ab initio molecular-dynamics calculations on atoms and molecules. For the case of oxygen, the transferability of the pseudopotential is demonstrated by comparing the calculated properties of molecular O2 and O3 with those obtained from conventional approaches. Converged results are obtained using plane-wave-basis cutoffs of only 25 Ry. Forces can be calculated efficiently, and a molecular-dynamics simulation of molecular vibration is demonstrated.