QUANTUM MONTE-CARLO OF NITROGEN - ATOM, DIMER, ATOMIC, AND MOLECULAR-SOLIDS

We have carried out variational and fixed-node diffusion Monte Carlo calculations for nitrogen in atomic, molecular, and compressed solid forms. This is the first work which treats the electron correlation in nitrogen solids with accuracy comparable to the most exact results on the atom and molecule. Comparison with local density approximation (LDA) calculations reveals LDA total energy errors varying from 2.1 eV in the atom to 0.7 eV/atom in the solid. We have also calculated the electronic energy gap for the compressed solid and compared it with the LDA (30% lower) and Hartree-Fock (100% higher) estimations.