Quantum Monte Carlo study of sodium

We report a variational and diffusion quantum Monte Carlo study of sodium. Pseudopotentials are used to represent the ion cores, and core-valence correlation effects are included by using a core polarization potential. When the core polarization potential is included we obtain an excellent value for the first ionization energy of the atom and a good value for the cohesive energy of the solid. Variational calculations of the occupied bandwidth give larger values than experiment, in agreement with recent sophisticated many-body calculations. Including the core polarization potential narrows the bandwidth slightly.