Overlap Integrals for Bloch Electrons

Overlap integrals of the modulating parts of Bloch functions are related to oscillator strengths and, by way of a sum rule, to effective masses and energy gaps. It is shown that in favourable cases this approach enables one to estimate overlap integrals more accurately than is possible by the use of wave functions obtained in the k. p approximation. Special attention is paid to the overlap between the conduction and the heavy hole band in InSb.