The Structure of Simple Glasses: Randomness
or Patternthe Debate Goes On*

P. H. Gaskell

Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK

Abstract—One question more than any other has focused the efforts of those working on the structure of
glasses. This is the extent to which the atomic structure can be considered to be uniform, continuous, with ran-
domness at the heart. Alternatively, is the structure essentially inhomogeneous, granular, with some close rela-
tionship to the structure of a neighboring crystalline phase? The question first received an answer for those sys-
tems that are prone to liquid–liquid immiscibility. But E.A. Porai-Koshits, among others, has not allowed the
question to settle there: the same issue applies to single-phase glasses. The topic is discussed against the back-
ground of work, mainly by the Cambridge group, on investigations by high resolution electron microscopy, neu-
tron scattering with isotopic substitution, and the connections between the detail in the low angle X-ray or neu-
tron scattering data to medium-range order in glasses on the scale of 0.5–1.5 nm—specifically, the relation
between low angle Bragg planes in the crystal and “quasi-Bragg” planes in the glass.

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