Low-temperature plasticity and lattice dynamics of solid parahydrogen with an isotopic impurity

The low-temperature plasticity of solid polycrystalline parahydrogen doped with an isotopic impurity (deuterium) is studied. The dependences of the rate of steady-state creep in p-H-2 on the impurity concentration and stress are obtained. The deformation of p-H-2 is described with inclusion of the zero-point mean-square displacements [x(2)] of particles making up a crystal. The calculated and experimental values of [x(2)] are compared for two possible isotope molecules (HD and D-2) at three stress levels. A correlation between the [x(2)] values and an increase in the force constants of a p-H-2 crystal doped with the isotopic impurity is established. An increase in the mean-square displacements of p-H-2 with the tensile load is discussed. Deformation-induced purification of a p-H-2 crystal from the isotopic impurity is suggested to occur. (C) 2003 MAIK "Nauka/Interperiodica".