CORRECTLY WEIGHTED TETRAHEDRON METHOD FOR K-SPACE INTEGRATION

The analytical integration of a linearly interpolated function commonly used in the tetrahedron integration (TI) method is not correct and the calculated quantities do not satisfy crystal symmetry. The authors propose an improved method wherein the integration is restricted to a minimal volume which covers the irreducible part of the Brillouin zone with microcubes in contrast to those by Kleinman (1983) and Hanke and co-workers (1984). They also extend this to a hexagonal crystal. The k-points in the correctly weighted TI method are shown to have the characteristics of special points and give accurate values for an insulator. The efficiency of the present method is discussed in comparison with the conventional TI method.