title: Structural and vibrational properties of K(3)Fe(MoO(4))(2)(Mo(2)O(7))-a novel layered molybdate.
abstract: The new compound K(3)Fe(MoO(4))(2)(Mo(2)O(7)) was synthesized and characterized by a single-crystal x-ray structure determination, and IR and Raman spectroscopic studies. The crystal structure at room temperature and ambient pressure is monoclinic, space group C 2/c, with the unit cell dimensions a = 32.885(7), b = 5.7220(11), c = 15.852(3) Å, β = 91.11°, Z = 8. The FeO(6) octahedra are joined by corners with MoO(4)(2-) tetrahedra and Mo(2)O(7)(2-) units. Some of the K(+) ions form layers in the b × c-plane. The origin of various Raman and IR vibrational modes is discussed. These results indicate that a clear energy gap exists between the stretching and remaining modes. High-pressure Raman scattering studies were also performed. These studies showed the onset of two reversible first-order phase transitions near 1.2 and 7.4 GPa, which are associated with strong distortion of the MoO(4)(2-) and Mo(2)O(7)(2-) units.
authors.affiliation: Institute of Low Temperature and Structure Research, Polish Academy of Sciences, PO Box 1410, 50-950 Wrocław 2, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Maczka
authors.forename: A
authors.initials: A
authors.lastname: Pietraszko
authors.forename: W
authors.initials: W
authors.lastname: Paraguassu
authors.forename: A G Souza
authors.initials: AG
authors.lastname: Filho
authors.forename: P T C
authors.initials: PT
authors.lastname: Freire
authors.forename: J Mendes
authors.initials: JM
authors.lastname: Filho
authors.forename: J
authors.initials: J
authors.lastname: Hanuza