Convergence of momentum space, pseudopotential calculations for Si

Using ab initio pseudopotentials for Si and the momentum-space formalism the convergence of the total energy with respect to all major cutoff parameters has been investigated. The calculations have been carried far enough that uncertainties due to cutoff can be estimated to be small. Using Ceperley and Alder's correlation energy, the calculated total energy and equilibrium lattice constant are smaller by 0. 023 Ry/atom and 0. 07, respectively, compared with experiment, whereas the use of the Wigner formula reduces these deviations by about a factor of 2.