LO-mode phonon of KCl and NaCl at 300 K by inelastic X ray scattering measurements and first principles calculations

TL;DR

This study combines inelastic X-ray scattering measurements and first-principles calculations to analyze LO phonon modes in KCl and NaCl at 300 K, revealing anharmonic effects and spectral features.

Contribution

It provides a detailed comparison of experimental and theoretical phonon spectra, highlighting anharmonicity effects in alkali halides.

Findings

Spectral functions show multiple peaks due to anharmonicity.

Calculated spectral functions offer higher resolution than IXS measurements.

LO modes along Γ–L paths are disconnected because of anharmonic effects.

Abstract

Longitudinal-optical (LO) mode phonon branches of KCl and NaCl were measured using inelastic X-ray scattering (IXS) at 300 K and calculated by the first-principles phonon calculation with the stochastic self-consistent harmonic approximation. Spectral shapes of the IXS measurements and calculated spectral functions agreed well. We analyzed the calculated spectral functions that provide higher resolutions of the spectra than the IXS measurements. Due to strong anharmonicity, the spectral functions of these phonon branches have several peaks and the LO modes along $\Gamma$--L paths are disconnected.