Raman scattering study of α-MgH2 and γ-MgH2

• Published in: Solid state communications Vol. 154; pp. 77 - 80
• Main Authors: Kuzovnikov, M.A., Efimchenko, V.S., Filatov, E.V., Maksimov, A.A., Tartakovskii, I.I., Ramirez-Cuesta, A.J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2013
• Subjects: A. Hydrides; B. High pressure; C. Raman scattering; C. Raman scattering; B. High pressure; A. Hydrides
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/j.ssc.2012.09.022

Two modifications of MgH2 have been studied by Raman spectroscopy: α-MgH2 with the P42/mnm space group and γ-MgH2 with the Pbcn space group. The latter was prepared from α-MgH2 by exposing it to a pressure of 5.6GPa at 470°C for 1.5h. A comparison of the experimental spectra with ab-initio calculations allowed identification of a few phonon modes. A broad feature in the Raman spectrum of α-MgH2 in the range 1470–1790cm−1 was identified as the B2g phonon mode. A Raman spectrum of γ-MgH2 consists of five discernible peaks at 186cm−1, 313cm−1, 509cm−1, 660cm−1, 706cm−1 and of three broad features in the regions 890–980cm−1, 1010–1220cm−1 and 1240–1430cm−1. The peaks are identified as the 1Ag (186cm−1), 3B3g (509cm−1), 2Ag (660cm−1) and 3B1g (706cm−1) phonon modes. ► A sample with a mass ratio of γ/(γ+α)>0.85 of the γ and α polymorphic phases of MgH2 is prepared under high pressure. ► Raman spectra of the γ and α polymorphs of MgH2 are measured at room temperature. ► Raman spectra of both polymorphs are computed using a DFT method. ► All intense peaks in the experimental Raman spectra of both polymorphs are assigned to the phonon modes.