Density functional study of the electronic and vibrational properties of TiOCl

TL;DR

This study uses hybrid density functional theory to analyze the phonon spectrum of TiOCl, revealing the importance of nonlocal correlations and explaining experimental observations of phonon anomalies related to its spin-Peierls phase.

Contribution

It provides a detailed phonon analysis of TiOCl across different phases using hybrid DFT, highlighting the role of nonlocal correlations in electron-lattice interactions.

Findings

Computed phonon frequencies match Raman and infrared data

Identified origin of anomalous Raman phonon

Linked high symmetry and low symmetry phonons in TiOCl

Abstract

We present the phonon spectrum of TiOCl computed using hybrid density functional theory (DFT). A complete analysis of the spectrum is performed for the space group Pmmn (high symmetry phase) and the space group P2_1/m (low symmetry phase), which is the symmetry of the spin-Peierls phase. We show that the nonlocal correlations present in the hybrid DFT approach are important for understanding the electron-lattice interactions in TiOCl. The computed frequencies compare well with those observed in Raman and infrared spectroscopy experiments and we identify the origin of an anomalous phonon observed in Raman spectroscopy. The relationship between relevant zone boundary phonons in the high symmetry phase and the zone center counterparts in the P2_1/m symmetry allow us to speculate about the origin of the spin-Peierls phonon.