Efficient and robust band-by-band conjugate-gradient (CG) methods for metallic systems with large unit cells and for band-structure calculations have been introduced to solve the Kohn-Sham (KS) equations within the framework of the pseudopotential plane-wave approach. These methods are very similar to the band-by-band CG scheme introduced by Teter, Payne, and Allan (TPA) [Phys. Rev. B 40, 12 255 (1989)]. In the present CG scheme used in band-structure calculations the KS equations, with the self-consistent potential, are solved by iteratively improving the wave functions by minimizing their corresponding eigenvalues. In the proposed CG method for metallic systems the wave functions of the occupied bands are updated as in the TPA approach, via total-energy minimization, and those of the unoccupied bands are updated as in the band-structure calculations. In this approach both the occupied and unoccupied bands are updated on equal footing, leading to an efficient and physically sound CG scheme. The introduced CG methods are applied to calculate the structural properties and the band structure of fcc copper.

• Received 17 August 1995

DOI:https://doi.org/10.1103/PhysRevB.52.14497