VIBRATIONAL SPECTRA AND FORCE CONSTANTS OF SPINELS.

Loading...
Thumbnail Image

Date

1969

Journal Title

Journal ISSN

Volume Title

Publisher

Ohio State University

Research Projects

Organizational Units

Journal Issue

Abstract

The spinels are a large family of compounds of general formula $A_{2}BX_{4}$. A is octahedrally coordinated and B is tetrahedrally coordinated. The space group is Fd3m, $O^{7}_{h}$ with 14 atoms in the primitive cell. A factor group analysis of the structure yields $A_{1g}(R)+E_{g}(R)+T_{1g} (inactive)+3T_{2g}(R)+2A_{2a} (inactive)+2E_{a} (inactive)+4T_{1u}(IR)+T_{1u}(acoustic)+2T_{2u}(inactive)$. Infrared and Raman spectra have been measured on a number of III-II, II-IV and I-VI spinels. (The Roman numerals refer to the valence states of the ions on the A and B sites respectively). A normal coordinate analysis of the structure has been performed using a simplified model containing only stretching force constants for the octahedral and tetrahedral bonds. Values of the tetrahedral force constant varies from 6.35 mdyne/\AA in $Na_{2}WO_{4}$ to 0.90 in $Cr_{2}CoO_{4}$. The octahedral force constants vary from $0.26 mdyne/\AA$ to 2.01 for the same compounds.

Description

$^{\ast}$ Present address of Bernardo A. DcAngelis: Gulf Research and Development Company, Harmarville, Pennsylvania.
Author Institution: Materials Research Laboratory, The Pennsylvania State University

Keywords

Citation