High-temperature thermodynamics of palladium–hydrogen. I. Dilute solutions of H2 and D2 in Pd at 555 K

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Abstract
The thermodynamic properties of palladium–hydrogen and palladium–deuterium solutions have been studied by a combined calorimetric–equilibrium method at 555 K for nH/nPd−1) and for deuterium (−1.80 kcal mol−1) we calculate from the Einstein model a vibrational frequency ν̃H for hydrogen in palladium of 695 cm−1, in reasonable agreement with the neutron scattering result for dilute solutions of Kley et al. (∼600 cm−1), but differing significantly from the much lower value of 420 cm−1 for PdH0.6 found by Bergsma and Goedkoop. The difference between the limiting values of the partial excess entropy of hydrogen (5.15 cal K−1⋅mol−1) and of deuterium (6.91 K−1⋅mol−1) is in excellent agreement with the value calculated from ν̃H and ν̃D=ν̃H/√2.