Calculated solution energies of heterovalent cations in forsterite and diopside: Implications for trace element partitioning

• Published in: Geochimica et cosmochimica acta 1997-09, Vol.61 (18), p.3927-3936
• Main Authors: Purton, J.A., Allan, N.L., Blundy, J.D.
• Format: Article
• Language: English
• ISSN: 0016-7037; 1872-9533
• DOI: 10.1016/S0016-7037(97)00198-1

Solution energies are calculated for a wide range of heterovalent impurities in forsterite and diopside, using atomistic simulation techniques and a consistent set of interatomic potentials to represent the non-Coulombic interactions between the ions. The calculations allow explicitly for ionic relaxation. Association between a charged defect and its compensating defect (s) cannot be neglected at low temperatures; however, at concentrations of 10–100 ppm a large proportion will be dissociated at temperatures above 1000 K. The variation of calculated solution energy with ion size reflects the variation in the relaxation energies, and often shows a parabolic variation with ionic radius. For the pure mineral, the calculated solution energies always show a minimum at a radius corresponding to that of the host cation; for impure clinopyroxene (with