SOLID PARADEUTERIUM - LATTICE-PARAMETERS AND THERMAL-EXPANSION

We have obtained for the first time systematic data on the lattice par ameters, the molar volume, the density, the x-ray thermal expansion of the high-temperature hcp phase of paradeuterium (x(f=1) = 0.86) in th e temperature range 4.5 to 18.5 K. By comparison with the previous res ults for orthodeuterium (x(f=1) = 0.025), we have determined how the q uadrupolar subsystem influences the structural (lattice parameters and volume) and thermodynamic (thermal expansion, Gruneisen constant) pro perties of deuterium. The quadrupolar pressure effect is shown to be t he highest at low temperatures, where the decisive contribution to the properties of crystals is given by the rotational subsystem.