Pressure-induced phase transformations in LiAlH4

Raja S Chellappa; Dhanesh Chandra; Stephen A Gramsch; Russell J Hemley; Jung-Fu Lin; Yang Song

doi:10.1021/jp060473d

Pressure-induced phase transformations in LiAlH4

J Phys Chem B. 2006 Jun 15;110(23):11088-97. doi: 10.1021/jp060473d.

Authors

Raja S Chellappa¹, Dhanesh Chandra, Stephen A Gramsch, Russell J Hemley, Jung-Fu Lin, Yang Song

Affiliation

¹ Metallurgical and Materials Engineering Division (MS 388), University of Nevada, Reno, Nevada 89557, USA.

PMID: 16771370
DOI: 10.1021/jp060473d

Abstract

The pressure-induced phase transformations in pure LiAlH4 have been studied using in situ Raman spectroscopy up to 7 GPa. The analyses of Raman spectra reveal a phase transition at approximately 3 GPa from the ambient pressure monoclinic alpha-LiAlH4 phase (P2(1)/c) to a high pressure phase (beta-LiAlH4, reported recently to be monoclinic with space group I4(1)/b) having a distorted [AlH4]- tetrahedron. The Al-H stretching mode softens and shifts dramatically to lower frequencies beyond the phase transformation pressure. The high pressure beta-LiAlH4 phase was pressure quenchable and can be recovered at lower pressures ( approximately 1.2 GPa). The Al-H stretching mode in the quenched state further shifts to lower frequencies, suggesting a weakening of the Al-H bond.