Soft pseudopotentials for efficient quantum Monte Carlo calculations: FromBe to Ne and Al to Ar

We have developed "soft" ab initio Hartree-Fock pseudopotentials for Be-Ne and Al-Ar that avoid singularities at the electron-nuclear cusp. The absenc e of these singularities is a desired feature for quantum Monte Carlo (QMC) calculations, because it considerably reduces local energy fluctuations wh en sampling the QMC wave function. A modified procedure for obtaining soft pseudopotentials is introduced. Stability of QMC calculations with the deve loped pseudopotentials is demonstrated by the ability to use larger time st eps for comparable accuracy with the previously available pseudopotentials. As expected, ionization potentials and electron affinities computed using the present approach compare very favorably with other Hartree-Fock pseudop otential methods. (C) 2001 American Institute of Physics.