  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.
