Influence of the Lattice and Electronic Factors on the Hydrogenation Properties of the RNi sub 5 -Base Haucke Compounds: Results of Low Temperature Heat Capacity Measurements

摘要

Low temperature heat capacities (1 to 20 exp 0 K) and the hydrogen absorption properties of some ternary Haucke compounds - LaNi/sub 5-x/Al/sub x/ (0 less than or equal to x less than or equal to 1.5), LaNi/sub 5-x/Pt/sub x/(0 less than or equal to x less than or equal to 5) and La/sub 1-x/Th/sub x/Ni sub 5 (0 less than or equal to x less than or equal to 1) - were investigated to examine any correlation between the ability of these compounds to absorb hydrogen and their physical properties - electronic structure and elastic properties. The density of states at Fermi level has a minimum near x = 1 in LaNi/sub 5-x/Al/sub x/, while the electronic specific heat constants of LaNi/sub 5-x/Pt/sub x/ decrease in a smooth fashion as the concentration of Ni decreases. However, La/sub 1-x/Th/sub x/Ni sub 5 alloys only exhibit a slight change in their electronic specific heat constants. The low temperature heat capacity was also measured on the hydrides of compounds above. The electronic specific heat constant, gamma , and Debye temperature, theta/sub D/, of the LaNi/sub 5-x/Al/sub x/H/sub y/ phase do not change as drastically, relative to the corresponding LaNi/sub 5-x/Al/sub x/ phase, as those for the RH sub 2 compounds relative to the corresponding pure metal, R. This is probably due to filling of the new bonding states formed in these compound hydrides with added electrons of hydrogen. (ERA citation 05:016166)