The infrared effective charge in IV-VI compounds. II. A three dimensional calculation

For pt.I see ibid., vol.12, no.21, p.4431, 1979. In order to explain the unusually large values of the transverse effective charge (Z T *) in cubic IV-VI compounds, Z T * was calculated using pseudopotential parameters derived from detailed three-dimensional band structure calculations; the results agree with experimental values to within 20%. This new technique is extremely simple and is not confined to IV-VI compounds. It requires only a knowledge of the pseudopotential form factors, without the calculation of wavefunctions, matrix elements, or band energies, which are cancelled out by the f sum rule. The transfer for IV-VI compounds validate the conclusions of the earlier simplified one-dimensional model.