Pressure‐Raman studies of layered alumino‐silicate compounds

We have conducted pressure‐Raman studies in order to understand the effects of structure on the vibrational properties of layered silicate materials. The basal oxygen torsional mode up‐shifts with pressure at a rate which agrees with that expected from a van der Waals force model. The pressure coefficient of the hydroxyl mode near 3600 cm⁻¹ is found to have a structurally dependent sign, stiffening for trioctahedral structures, softening for dioctahedral silicates. This is found to be associated with hydroxyl orientation and coulombic repulsion between the hydroxyl proton and the interlayer cation.