Gladstone–Dale compatibility, electronic polarizability and vibrational spectroscopy of minerals and inorganic compounds with V4+O and V4+O2 vanadyl groups

Abstract

VO and VO2 vanadyl groups with short (typically 1.57–1.68 Å), essentially covalent, V—O bonds are common for V4+-bearing oxysalts with [5]- and [6]-coordinated vanadium. There is a clear negative correlation between vanadyl bond lengths and wavenumbers of the bands of V—O stretching vibrations in infrared spectra (in the range 1000–880 cm−1). Optical, structural and chemical data for vanadyl minerals are used to calculate Gladstone–Dale compatibility coefficients. Gladstone–Dale compatibility indices of minerals containing vanadyl bonds are compared with total electronic polarizabilities of V4+. Unlike compounds of [5]-coordinated Ti4+, for most minerals with V4+=O (vanadyl) bonds there is good agreement between measured refractive indices and those calculated based on the polarizability concept.