Variations of bond lengths and volumes of silicate tetrahedra with temperature

The apparent SiO bond lengths recorded for silicates over a range of temperatures either typically are invariant or exhibit a contraction with increasing temperature. A rigid-body thermal analysis was completed for the tetrahedra in nine silicates whose structures have been determined over a range of temperatures from 15 to 1250 K and whose tetrahedra seem to behave as rigid units. The bond lengths and volumes estimated for tetrahedra with four bridging O atoms seem to increase with temperature at a faster rate than those with four nonbridging O atoms. Those for tetrahedra with two or three nonbridging O atoms tend to increase an an intermediate rate. -from Authors