Structural-energy calculations based on norm-conserving pseudopotentials and localized Gaussian orbitals

The total energy, equilibrium lattice constant, and bulk modulus are calculated for diamond, silicon, and GaP. These ground-state calculations are carried out in a localized Gaussian basis (20 orbitals per atom) using a real-space formalism devised for defect crystal studies. High-precision norm-conserving pseudopotentials simulate the interaction of the valence electrons with the atomic cores. The results are typically within 1-4% of experiment, which is not good enough to determine absolute cohesive energies but should be sufficient for studies of structural deformations and elastic properties. An analysis and comparison with other calculations show that the errors arise predominantly from the use of a minimum local-orbital basis and not from pseudopotentials.