ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The heat capacity at constant pressure, Cp, of single-phase, face-centered cubic ScDx (x=1.75, 1.83, 1.91, and 1.99) was measured from room temperature to 950 K, and analyzed in terms of various contributions of the deuterium and metal constituents. Values ranged from approximately 40 to 80 J mol−1 K−1 with increasing temperature. The heat capacity at constant volume was assumed to be composed of lattice contributions from an acoustic vibrational mode, Cl(a)v, and an optical vibrational mode, Cl(o)v, plus an electronic contribution, Cev. The acoustic part, Cl(a)v, was evaluated as a Debye term with characteristic Debye temperatures calculated from measured values of temperature-dependent acoustic velocities and lattice constants. An isotope-adjusted Einstein temperature, derived from inelastic neutron scattering measurements on ScH2, was used to find Cl(o)v. The Cev term was evaluated from a published value of the electronic heat capacity constant for ScH2 (assumed to be the same for ScD2). Particular attention was paid to the dilation term, Cd=Cp−Cv, by evaluating it explicitly from the temperature-dependent volume expansion and elastic modulus. It was found that Cv=Cl(a)v+Cl(o) v+Cev+ΔC, the last term being an excess heat capacity of approximately the same magnitude as Cd. ΔC is attributed to anharmonic deuteron vibrations and deuteron–deuteron interactions, and is calculated for a specific model in reasonable agreement with the data.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.450542
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