Early in this century, the newly discovered x-ray diffraction by crystals caused a complete change in crystallography and in the whole science of the atomic structure of matter, thus giving a new impetus to the development of solid-state physics. Crystallographic methods, primarily x-ray diffraction analysis, pene- trated into materials sciences, molecular physics, and chemistry, and also into may other branches of science. Later, electron and neutron diffraction structure analyses became important since they not only complement x-ray data, but also supply new information on the atomic and...