Transport and thermodynamic properties under anharmonic motion in type-I Ba8Ga16Sn30 clathrate

TL;DR

This study investigates how anharmonic guest atom oscillations in Ba8Ga16Sn30 clathrates affect thermal and electrical properties, revealing insights into local excitations and potential energy landscapes through combined experimental and theoretical analysis.

Contribution

It provides a comprehensive analysis of anharmonic oscillations' impact on physical properties, integrating heat capacity, transport measurements, and NMR data to elucidate local oscillator distributions and potentials.

Findings

Good agreement between anharmonic rattler potential and experimental data

Localized anharmonic excitations influence low-temperature resistivity

Heat capacity reflects the excitation level structure

Abstract

Anharmonic guest atom oscillation has direct connection to the thermal transport and thermo- electric behavior of type-I Ba8Ga16Sn30 clathrates. This behavior can be observed through several physical properties, with for example the heat capacity providing a measure of the overall excita- tion level structure. Localized anharmonic excitations also influence the low-temperature resistivity, as we show in this paper. By combining heat capacity, transport measurements and our previous NMR relaxation results, we address the distribution of local oscillators in this material, as well as the shape of the confining potential and the excitation energies for Ba(2) ions in the cages. We also compare to the soft-potential model and other models used for similar systems. The results show good agreement between the previously deduced anharmonic rattler potential and experimental data.