Raman scattering study of NaAl(MoO4)2 crystal under high pressures

• Published in: Journal of physics. Condensed matter Vol. 16; no. 28; pp. 5151 - 5161
• Main Authors: Paraguassu, W, Filho, A G Souza, Maczka, M, Freire, P T C, Melo, F E A, Filho, J Mendes, Hanuza, J
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 21.07.2004; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Infrared and raman spectra and scattering; Lattice dynamics; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other nonmetallic inorganics; Phonon states and bands, normal modes, and phonon dispersion; Phonons and vibrations in crystal lattices; Physics; Sodium Molybdates; Raman spectra; Ferroelastic materials; Inorganic compounds; Pressure effects; Phase transformations; Lattice dynamics; Vibrational modes; Aluminium Molybdates; Experimental study; Quaternary compounds; High pressure
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/16/28/033

The high-pressure Raman spectra of ferroelastic NaAl(MoO4)2 have been measured at room temperature. The studies indicated that this crystal exhibits two pressure-induced phase transitions at about 1.1 and 3.3 GPa. The first transition is connected with slight rotation of the MoO4-2 tetrahedra with loss of the inversion centre. The second transition is connected with significant distortion of the MoO42- tetrahedra and Al3+ coordination sphere. By performing the lattice dynamics calculations in the starting phase (monoclinic C2h6) we have been able to make an assignment of the Raman modes of this material. The deep knowledge of the modes helped us to get fundamental insights into the mechanism driving the structural changes occurring in NaAl(MoO4)2. The two phase transitions observed in the 0.0-4.2 GPa pressure range are completely reversible.