Europhys. Lett.
Volume 64, Number 3, November 2003
Page(s) 344 - 350
Section Condensed matter: structure, mechanical and thermal properties
Published online 01 December 2003
DOI: 10.1209/epl/i2003-00187-x
Europhys. Lett., 64 (3) , pp. 344-350 (2003)

Tetrahedral occupancy in the $\chem{Pd}$- $\chem{D}$ system observed by in situ neutron powder diffraction

M. P. Pitt and E. MacA. Gray

School of Science, Griffith University - Brisbane 4111, Australia

(Received 16 April 2003; accepted in final form 29 August 2003)

The crystallography of the $\chem{Pd}$- $\chem{D}$ x system has been studied by in situ neutron powder diffraction at 309 $\un{{}^{\circ}C}$, in the supercritical region, and, after quenching in the pure $\beta$ phase to 50 $\un{{}^{\circ}C}$, in the two-phase region at 50 $\un{{}^{\circ}C}$. Rietveld profile analysis of the supercritical diffraction patterns showed that 14% of D interstitials were occupying tetrahedral interstices, in sharp contrast to previous studies at lower temperatures. Tetrahedral occupancy was maintained through the two-phase region at 50 $\un{{}^{\circ}C}$. These results are discussed in the light of first-principles total-energy calculations of hydrogen states in palladium.

61.50.Ks - Crystallographic aspects of phase transformations; pressure effects.
61.72.Dd - Experimental determination of defects by diffraction and scattering.
61.72.Ji - Point defects (vacancies, interstitials, color centers, etc.) and defect clusters.

© EDP Sciences 2003