Structural Study of Thermoelectric Clathrate Ba8Al16-xGaxGe30

We study the effects of the Al substitution by Ga on the crystal structures of type I clathrate Ba
₈
Al
_16-x
Ga
_x
Ge
₃₀
(x = 2, 4, 6, and 8) by neutron powder diffraction. The diffraction data were refined using two models for Ba guest atom position in the oversized cage (Ba2): on center (6d site) and off-center (24k site) model. We also carried out the Maximum Entropy Method (MEM) analysis. The 24k model is in a good agreement with the Maximum Entropy Method (MEM) results. The evolution of nuclear density distribution with increasing temperature of Ba
₈
Al
₈
Ga
₈
Ge
₃₀
was revealed by MEM analysis.