Quartic Anharmonicity of Rattlers and Its Effect on Lattice Thermal Conductivity of Clathrates from First Principles

We investigate the role of the quartic anharmonicity in lattice dynamics and thermal transport of type-I clathrate Ba_{8}a_{16}e_{30}based on \textit{ab initio} self-consistent phonon calculations. We show that the strong quartic anharmonicity of rattling guest atoms causes the hardening of vibrational frequencies of low-lying optical modes and thereby affects calculated lattice thermal conductivities \kappa_{L}significantly,...