Influence of dipole interaction on lattice dynamics of crystalline ice

TL;DR

This study investigates how dipole interactions influence the lattice dynamics of crystalline ice by calculating phonon spectra and Born effective charges using first-principles methods, revealing LO-TO splitting consistent with experimental data.

Contribution

It introduces a correction to phonon calculations that accounts for dipole interactions, enhancing understanding of polar mode splitting in ice.

Findings

Evidence of LO-TO splitting at k=0 in ice

Agreement with experimental observations of phonon modes

Demonstration of dipole effects on lattice dynamics

Abstract

The Born effective charges of component atoms and phonon spectra of a tetrahedrally coordinated crystalline ice are calculated from the first principles method based on density functional theory within the generalized gradient approximation with the projected augmented wave method. Phonon dispersion relations in a 3x1x1 supercell were evaluated from Hellmann-Feynman forces with the direct method. This calculation is an additional work to the direct method in calculating the phonon spectra which does not take into account the polarization charges arising from dipole interaction of molecules of water in ice. The calculated Born effective polarization charges from linear response theory are supplied as the correction terms to the dynamical matrix in order to further investigate the LO-TO splitting of the polar modes of ice crystal at k=0 which has long been speculated for this system especially in the region between 28 and 37 meV both in the theoretical and experimental studies. Our results clearly show the evidence of splitting of longitudinal and transverse optic modes at the k=0-point in agreement with some experimental findings.