THEORETICAL STUDY OF RATTLING ATOMS AND THIER INFLUENCE ON
THE LATTICE THERMAL CONDUCTIVITY IN CLATHRATE-FRAMEWORK
SEMICONDUCTORS
Otto F. Sankey1, Jianjun Dong2, and Charles W. Myles3,
1
Arizona State University, Tempe, AZ 85287-1504
2
Auburn University, Auburn, AL 36849-5311;
3
Texas Tech University, Lubbock TX 79409-1051
We have explored the electronic and vibrational properties of type-I and type-II
semiconductor (Si, Ge, and Sn) clathrates using theoretical DFT electronic structure methods.
These framework materials have open cages which harbor guest impurities, and produce local
vibrational modes. We search for trends in the vibrational frequencies of the guest modes, and
compare them to experiment. These modes may scatter the extended heat-carrying acoustic modes.
We have investigated the effect of guests on the lattice thermal conductivity by evaluating the
linear response theory heat current correlation functions using molecular dynamics. We compare
these results to results of guest-free crystals, and to amorphous materials. Our results are consistent
with experiments, and have impact as a theoretical test of the “rattler” concept.