Unusual changes in the shape of solid parahydrogen with higher than natural isotope content.

The relative elongation f. of samples of high purity (99.9999 mol. % with respect to nonhydrogenic impurities) parahydrogen (p-H2, ~0.2% o-H2) with different amounts of the stable hydrogen isotope deuterium is measured as a function of applied stress σ at temperatures of 1.8-4.2 K. The samples were subjected to uniaxial tension by stepwise loading. The ratio [D]/[H] of the number [D] of deuterium atoms to the number [H] of p-H2 hydrogen atoms ranged from 0.0055 ± 0.0005 at. % up to 0.07 at. %. For deuterium enriched p-H2, the easy slip dislocation stage vanished from the σ(ε) curves and there was a significant reduction in the total relative elongation of the samples, as well as a substantial increase in the hardening coefficient dσ/dε. Deformation of samples of p-H with deuterium contents higher than the natural amount produces an unusual change in their shape owing to the appearance of a rotational component of the low-temperature plastic mass transfer. [ABSTRACT FROM AUTHOR]