INFORMATION-CONTENT OF DIFFRACTION EXPERIMENTS ON LIQUIDS AND AMORPHOUS SOLIDS

Starting with simple monatomic liquids such as condensed rare gases, the information that can be extracted from diffraction experiments is discussed. The rich interplay between atomic and electronic structure in liquid metals such as Na and K is emphasized: expanded Rb and Cs taken up the liquid-vapour coexistence curve towards the critical point are also mentioned. A liquid metal like Na is, in fact, a two-component system, Na+and electrons. Classical two-component systems are also considered, and specifically BaCl2which freezes into a fast-ion conducting phase. The structural theory of two-component liquids is extended to apply to amorphous Si, the ‘second component’ now being the bond charge. The way a combination of X-ray and electron diffraction can elucidate the nature of the local ordering, as well as the directional bonding, is stressed. There is clear evidence here for the bonding electrons, directly from the X-ray and electron scattering intensity. © 1990, Taylor & Francis Group, LLC. All rights reserved.