Investigation of structure and hydrogen bonding of super-hydrous phase B (HT) under pressure using first principles density functional calculations

TL;DR

This study uses first principles density functional theory calculations to analyze the high-pressure structural and hydrogen bonding changes in super-hydrous phase B, revealing cooperative distortions and challenging previous bond bending models.

Contribution

It demonstrates the effectiveness of first principles calculations in understanding pressure-induced bonding and structural changes in complex mineral phases.

Findings

Hydrogen bonds undergo cooperative distortions under pressure.

The bond bending mechanism is not effective in super-hydrous phase B.

O-H bond contraction correlates with blue shift in stretching frequency.

Abstract

High pressure behaviour of superhydrous phase B(HT) of Mg10Si3O14(OH)4 (Shy B) is investigated with the help of density functional theory based first principles calculations. In addition to the lattice parameters and equation of state, we use these calculations to determine the positional parameters of atoms as a function of pressure. Our results show that the compression induced structural changes involve cooperative distortions in the full geometry of the hydrogen bonds. The bond bending mechanism proposed by Hofmeister et al [1999] for hydrogen bonds to relieve the heightened repulsion due to short H--H contacts is not found to be effective in Shy B. The calculated O-H bond contraction is consistent with the observed blue shift in the stretching frequency of the hydrogen bond. These results establish that one can use first principles calculations to obtain reliable insights into the pressure induced bonding changes of complex minerals.