High-temperature thermodynamics of the Ti--H$sub 2$ and Ti--D$sub 2$ systems

Journal Article · Thu Jan 01 04:00:00 EST 1976 · J. Chem. Phys., v. 64, no. 1, pp. 139-147

OSTI ID:4094302

Dantzer, P; Kleppa, O J; Melnichak, M E

The high-temperature thermodynamic properties of the Ti+H$sub 2$ and Ti+D$sub 2$ solid systems have been studied by a combined calorimetric and equilibrium method at 706--721 K (both systems) and 971 K (Ti+H$sub 2$ only). The limiting enthalpies of solution of hydrogen in close-packed hexagonal $alpha$- Ti is -10.6 kcal mole$sup -1$(H) at the lower temperature, and about -10.9 kcal mole$sup -1$(H) at the higher temperature. The corresponding value of $delta$H/ sub D/ at 707 K is -10.1 kcal mole$sup -1$(D). From the hydrogen and deuterium data at 707--721 K we estimate nu-tilde/sub H/ in $alpha$--Ti to be about 800 cm$sup -1$ and nu-tilde/sub D/ about 565 cm$sup -1$. The equilibrium pressures and the partial enthalpies of hydrogen and deuterium allow an evaluation of the partial entropies and excess entropies, S/subE//sub H/ and S/subE//sub D/. The limiting value of S/subE//sub H/ at N/sub H/approx. =0 and 706--721 K is 6.5 cal K$sup -1$xmole$sup -1$(H), that of S/subE//sub D/ at the same temperature is 8.9 cal K$sup -1$xmole$sup -1$(D). These values are larger than corresponding values calculated from nu-tilde/sub H/ and nu-tilde/sub D/. This discrepancy suggests either much lower vibrational frequencies (than calculated from $delta$H/sub H/ and $delta$H/sub D/), or perhaps a very significant communal entropy term. (AIP)

• Research Organization: The James Franck Institute and Department of Chemistry, The University of Chicago, Chicago, Illinois 60637
• NSA Number: NSA-33-019698
• OSTI ID: 4094302
• Journal Information: J. Chem. Phys., v. 64, no. 1, pp. 139-147, Journal Name: J. Chem. Phys., v. 64, no. 1, pp. 139-147; ISSN JCPSA
• Country of Publication: United States
• Language: English

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