Lines of formation and decomposition of the hcp(ε) molybdenum deuteride in the T-P phase diagram of the MoD system are constructed via the measurement of isotherms of the electrical resistance of molybdenum in a deuterium atmosphere at temperatures up to 550 • C and pressures up to 6 GPa. The diagram is compared to that of the Mo-H system studied earlier. The pressure of phase equilibrium in both systems is shown to be much closer to the decomposition pressure than to the formation pressure. A new explanation is suggested for this asymmetry in the hysteresis loop that seems to be characteristic of many metal-hydrogen systems. From the position of the decomposition lines, the standard entropy, enthalpy and Gibbs energy of formation are estimated for molybdenum deuteride and hydride.

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structure structure (solids and liquids) D 2000 -007The Crystal Structure of Nb 3 AuHx.-The Nb 3 AuHx compounds with x = 2.9 (I) and x = 4.2 (II) are prepared by exposing the starting alloy Nb 2.96 Au 1.04 (III) to hydrogen pressures of 0.85 and 5.1 GPa, resp., at 325 • C for 24 h. The XRD analysis of (III) shows that, in addition to the Nb 2.98 Au 1.02 phase (A15 structure, Pm3n, Z = 2), the sample contains the two impurity phases Nb 3 Au 2 and Nb 11 Au 9 . The crystal structures of (I) and (II) belong to the cubic system, space group Pm3n (neutron diffraction). -(ANTONOV, V. E.; BOKHENKOV, E. L.; DORNER, B.; FEDOTOV, V. K.; GROSSE, G.; LATYNIN, A. I.; WAGNER, F. E.; WORDEL, R.; J. Alloys Compd. 264 (1998) 1-2, 1-7; Inst. Phys.