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The Nature of Deuterium Arrangements in YD3 and other Rare-Earth Trideuterides

Published

Author(s)

Terrence J. Udovic, Qingzhen Huang, Antonio Santoro, John J. Rush

Abstract

The efficacy of different structural models for describing the observed neutron-powder-diffraction (NPD) measurements of bulk polycrystalline YD3 as well as other hexagonal rare-earth (i.e., Nd, Tb, Dy, Ho, Er, and Tm) trideuteride powders has been investigated via Rietveld refinement. Between the two possible structural configurations, centrosymmetric P3c1 and noncentrosymmetric P63cm, the latter can be excluded due to very high correlations found between the positions of the D sites. Hence, the true "diffraction-average" structure for YD3 and all other rare-earth deuterides studied is centrosymmetric (P3c1). This seems to contrast with the prior evidence from first-principles calculations and various spectroscopic probes suggesting that the true local symmetry is not P3c1, but rather, noncentrosymmetric. A possible way to reconcile the apparently conflicting conclusions from NPD and spectroscopic measurements is by assuming that the real structure is a twinned arrangement of nanosized, noncentrosymmetric configurations. For example, we demonstrate that the diffraction-average centrosymmetric P3c1 structure can result from a superposition of individual, noncentrosymmetric P3c1 twins. A comparison of neutron vibrational spectra for YH3 and YD3 confirms that both compounds share similar structural arrangements.
Citation
Zeitschrift Fur Kristallographie
Volume
223
Issue
10

Keywords

diffraction, lanthanum trifluoride, neutron powder diffraction, neutron scattering, neutron spectroscopy, rare-earth deuteride, twinning, vibrational spectroscopy, yttrium trideuteride

Citation

Udovic, T. , Huang, Q. , Santoro, A. and Rush, J. (2008), The Nature of Deuterium Arrangements in YD3 and other Rare-Earth Trideuterides, Zeitschrift Fur Kristallographie, [online], https://doi.org/10.1524/zkri.2008.1139, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=610011 (Accessed April 19, 2024)
Created September 30, 2008, Updated March 21, 2024