First-principles, general-potential local-orbital calculations for bulk crystals

We describe a first-principles computational technique for calculating electronic structure, using the method of linear combination of atomic orbitals (LCAO). Gaussian-type orbitals are used, so that all matrix element integrals are calculated analytically. The technique makes no shape approximations to either the charge density or the effective one-electron potential, aside from the usual local-density approximation to the exchange-correlation potential. We have applied the method to three qualitatively different systems: diamond, vanadium, and a diamond-nickel (001) ideal interface supercell. To assess the accuracy of this technique, we have performed parallel calculations using the linear augmented-plane-wave (LAPW) method. In this way, all possible discrepancies due to choice of lattice constant and exchange-correlation potential are removed. Detailed comparisons between the LCAO and LAPW results for all three systems are made. Overall agreement between the two methods is excellent.