From disordered crystal to glass - exact theory

We calculate thermodynamic properties of a disordered model insulator, star ting from the ideal simple-cubic lattice (g = 0) and increasing the disorde r parameter g to much greater than 1/2. As in the earlier Einstein and Deby e approximations, the ground state energy is discontinuous at g(c) = 1/2. F or g < g(c) the low-T heat-capacity C similar to T-3, whereas for g > g(c), C similar to T. The van Hove singularities disappear at any finite magnitu de g of the disorder. For g > 1/2 we discover novel fixed points in the sel f-energy and spectral density of this model glass. (C) 2001 Elsevier Scienc e B.V. All rights reserved.