Orientational quadrupolar glass in ortho-para hydrogen mixtures. I. Mean-field microscopic theory

Abstract

The mean-field theory of the quadrupolar glass (QG) is presented using a microscopic approach. It is shown that the reaction-polarization effects caused by short-range spatial correlations are well distinguished from those of random-bond spin glasses. They control the QG concentration threshold and result in an incomplete orientational order. The QG ground state (zero quadrupolization, unsaturated Edwards-Anderson-type orientational order parameter) is predicted. Thermodynamic characteristics, namely entropy, pressure and free energy as well as the related heat capacity and Gruneisen parameter are estimated. The ground-state findings (incomplete order, residual entropy) are similar to those of short-range Potts glasses. A correspondence between density matrix and mean field treatment to the QG problem is also discussed.