Empty-lattice test of the linearized atomic-cell orbital method for energy bands

The linearized atomic-cell orbital (LACO) method is used to compute free-electron energy bands. Variational calculations are carried out for a Wigner-Seitz atomic cell appropriate to the fcc Cu lattice, and are compared with exact free-electron energy bands along the K line. Spherical harmonics through l=4 are included in full polyhedral calculations. For comparison, calculations using a spherical approximation are carried through l=5. Results show that the LACO method is efficient and accurate. It converges more rapidly than the spherical approximation. © 1987 The American Physical Society.