The evaluation of the energy of formation of point defects in silicates is developed using solid-state theory. The calculations require a proper treatment of the polarization effects in the crystal as well as the usual Coulomb and repulsion energy terms. The theory is apphed to the calculation of point defects in forsterite. The Mg–O and O–O repulsion potential calculation uses the recent electron gas theory of Gordon and Kim (1972). The partly covalent Si–O bond is treated semi-empirically. The relative importance of the various energy terms in the overall energy of formation is evaluated. The results show a marked difference between defects on the M1 and M2 octahedral sites, and among the three different oxygen sites of olivine. The energy differences are on the order of several electron volts. The implication of the results on the nature of defects and on the diffusion mechanism in olivines is then treated.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not have access to this content, please speak to your institutional administrator if you feel you should have access.