Low-temperature heat-capacity study of Haucke compounds Ca Ni 5 , Y Ni 5 </mml:…
1980; American Physical Society; Volume: 21; Issue: 12 Linguagem: Inglês
10.1103/physrevb.21.5636
ISSN1095-3795
AutoresToru Takeshita, K. A. Gschneidner, D. K. Thome, O.D. McMasters,
Tópico(s)Advanced Chemical Physics Studies
ResumoLow-temperature heat capacities of some Haucke compounds (Ca${\mathrm{Ni}}_{5}$, Y${\mathrm{Ni}}_{5}$, La${\mathrm{Ni}}_{5}$, and Th${\mathrm{Ni}}_{5}$) were studied. The electronic specific-heat constants of these compounds are nearly the same and slightly smaller than that of pure nickel. The Deybe temperatures of these compounds show a wider variation than the electronic specific-heat constants. It is found that the lattice rigidity of these four compounds varies considerably, with that of La${\mathrm{Ni}}_{5}$ being the softest, followed by Ca${\mathrm{Ni}}_{5}$, Th${\mathrm{Ni}}_{5}$, and Y${\mathrm{Ni}}_{5}$ in order of increasing rigidity. This appears to influence their hydrogen absorption capacity. The relative softness is correlated with the Ni-Ni distances in the midplane [$3(g)$ sites], and it is suggested that the Ni atoms in this plane play a critical role in governing the hydrogenation behavior of these materials.
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