-1- Quadrupolar Glass State in para-hydrogen and ortho-deuterium under pressure.

Quadrupolar Glass State in para-hydrogen and ortho-deuterium under pressure. The main features of the possible quadrupolar glass state in ortho-deuterium and para-hydrogen under high pressure are predicted and considered in replica-symmetric approximation in analogy with glassy behavior of diluted ortho-hydrogen at low pressures. The quadrupolar model with J = 2 is suggested. The orientational order and glass regime grow continuously on cooling just as it is in the case of ortho-para hydrogen mixtures at zero pressure. The structure of high pressure phases of solid hydrogen has been widely investigated recently (e.g. [1, 2, 3]). At low pressures, the centers of para-hydrogen and ortho-deuterium molecules occupy the lattice sites of the hcp structure. The molecules are in spherically symmetric states (phase I or SP). Between 28 Gpa for o-D 2 and 110 Gpa for p-H 2 and ~150 Gpa the molecules become orientationally ordered in broken-symmetry phase II (BS). High pressure breaks the rotational symmetry of the J=0 solids. The ordering occurs even in the systems of para-hydrogen and ortho-deuterium molecules because of mixing of higher order J levels with the ground state J = 0 as a result of the increase of the intermolecular interactions at high pressures [1,2]. The anisotropic interaction between two molecules is