Isotopic effects in the phonon and electron dispersion relations of crystals

During the past ten years, the relaxation of international tensions between East and West has resulted in the so-called "peace dividends". Among these dividends, solid state physicists have profiled from the increasing availa bility of stable isotopes of many elements at affordable prices. These isot opes originate sometimes in the United States and sometimes in Russia. They can either be purchased or obtained "on loan" on the basis of scientific c ollaboration. With these isotopes, single crystals with tailor-made isotopi c compositions have been grown. Using these crystals, information on a numb er of rather basic physical properties has been obtained. We discuss in thi s review the following properties of such semiconductor crystals: 1. depend ence of the lattice parameters on isotopic masses; 2. effect of isotopic di sorder on thermal conductivity; 3. anharmonic effects on the phonon frequen cies and linewidths and their dependence on isotopic mass; 4. effects of is otopic disorder on phonon frequencies and linewidhts; 5. renormalization of the energy of electronic states through electron-phonon interaction; and 6 . self-diffusion of atoms in crystals. Because of space limitations this di scussion will not be exhaustive. We hope, however, to give sufficient refer ences to published work so that the interested reader can easily find the p rimary literature sources to this rapidly expanding field of solid state ph ysics. (A few multilingual short reviews are listed under [1].)