May 1

Abstract

Considerable progress has been made during recent years in the study of the electronic band structure of crystalline solids. This is partly due to newly developed, efficient methods of calculation and the increasing use of fast computers. On the experimental side the measurement of the optical absorption and reflectivity spectra of many insulators, semiconductors, and metals - more recently also with external symmetry reducing parameters applied simultaneously - have in conjunction with the calculated band models provided a great deal of information about the dispersion of energy bands in fc-space. Whereas in the beginning the interest was concentrated on materials with cubic crystal structure, now increasing numbers of crystals of lower symmetry are also under study.