Pressure effects on hydrogen atoms near the metal plane in the HCP phase of rare-earth metal trihydrides. (April 2016)

• Record Type: Journal Article
• Authors: Tunghathaithip, N.; Pakornchote, T.; Phaisangittisakul, N.; Bovornratanaraks, T.; Pinsook, U.
• Is Part Of: Solid state communications. Volume 231/232(2016)
• Page Start: 48
• Page End: 52
• Publication Date: 2016-04
• Subjects: A. Semiconductor -- C. Crystal structure and symmetry -- D. Phonon; Solid state chemistry -- Periodicals; Solid state physics -- Periodicals; Chimie de l'état solide -- Périodiques; Physique de l'état solide -- Périodiques; 530.41
• DOI: 10.1016/j.ssc.2016.01.018
• Languages: English
• ISSNs: 0038-1098

Abstract

Abstract: Rare-earth metal trihydrides, REH3 (RE=Sc, Y, La), in the hcp phase were investigated under high pressure by the ab initio method. We concentrated on the behavior of hydrogen atoms which is affected by pressure. Two-thirds of the hydrogen atoms near the metal plane (H m ) were found to displace away from the metal plane as pressure increases. The trajectory of these squeezed hydrogen atoms is from a site near the metal plane, and moves past the plane of the tetragonal sites, and heads toward the nearest octahedral site. However, the rate of displacement depends on the local environment. LaH3 exhibits the least impediment on the H m displacement while YH3 and ScH3 exhibit stronger impediment. Furthermore, our calculated Raman and IR active modes are in general agreement with the experimental data. The displacement of H m can be used to explain the behavior of the O v peak in Raman spectra, where it exists at low pressure and disappears at higher pressure in YH3 and ScH3 . Abstract : Highlights: Behavior of H atoms in hcp phase of rare-earth metal trihydrides under high pressure. H atoms move away from metal plane by reducing of interval between metal atoms. Strength of impediment of hydrogen movement increases in a sequence; LaH 3 → YH 3 → ScH 3 . H behavior effects to softening shift of Raman and IR spectra by pressure.