Electronic structure and total-energy calculations by a semi-self-consistent augmented-plane-wave method.

We have adopted the Harris functional approximation in a standard framework of augmentedplane-wave (APW), density-functional calculations. Our implementation of the Harris approximation is based on a charge density from a self-consistent APW band-structure calculation for one lattice constant. This charge density is then frozen for calculation of the electronic structure and total energy at other lattice constants and for other crystal structures. The advantage of this approach over standard implementations of the Harris approximation is that our scheme computes the correct band structure as well as the correct total energy. We have applied this scheme to a wide variety of materials, ranging from transition metals to binary and ternary compounds. We present several examples and use these examples to motivate discussions of the scheme. Using this method, we have calculated total energies, equilibrium lattice constants, and bulk moduli which are in very good agreement with self-consistent results.