Spontaneous Anisotropy in Cubic Thermoelectric GeTe

June 15, 2023
Spontaneous Anisotropy in Cubic Thermoelectric GeTe
Structure factors for total energy integrated (instantaneous) and elastic (time-averaged) scattering of GeTe at 720 K. The extra oscillation in the instantaneous data shows that the apparent 2.88 Å real-space splitting is dynamic.

Scientific Achievement

The high temperature thermoelectric material GeTe exhibits no long-range disorder, but instead develops spontaneous anisotropic correlated atomic motions disrupting thermal conductivity.

Significance and Impact

Understanding dynamic disorder in materials could lead to more energy-efficient solid-state devices, like heat pumps, thermoelectric generators, and refrigerators. This work resolves the long-standing disagreement between local and average structure probes. 

Research Details

  • The novel variable-shutter pair distribution function (vsPDF) technique reveals the difference between instantaneous (energy integrated) and time-averaged (elastic) real space atomic correlations.
  • Combining ab initio molecular dynamics calculations with inelastic neutron scattering simulations identified specific vibrational modes involved.

“Dynamic crystallography reveals spontaneous anisotropy in cubic GeTe”
Simon A. J. Kimber , Jiayong Zhang , Charles H. Liang, Gian G. Guzmán-Verri , Peter B. Littlewood, Yongqiang Cheng , Douglas L. Abernathy , Jessica M. Hudspeth , Zhong-Zhen Luo , Mercouri G. Kanatzidis , Tapan Chatterji, Anibal J. Ramirez-Cuesta and Simon J. L. Billinge,
Nature Materials 22, 311-315 (2023), DOI: ARCS