Unraveling the origins of conduction band valley degeneracies in Mg2Si1-xSnx thermoelectrics

Chang Eun Kim, Aloysius Soon, Catherine Stampfl

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

To better understand the thermoelectric efficiency of the Mg-based thermoelectrics, using hybrid density-functional theory, we study the microscopic origins of valley degeneracies in the conduction band of the solid solution Mg2Si1-xSnx and its constituent components - namely, Mg2Si and Mg2Sn. In the solid solution of Mg2Si1-xSnx, the sublattices are expected to undergo either tensile or compressive strain in the light of Vegard's law. Interestingly, we find both tensile strain of Mg2Si and compressive strain of Mg2Sn enhance the conduction band valley degeneracy. We suggest that the optimal sublattice strain as one of the origins of the enhanced Seebeck coefficient in the Mg2Si1-xSnx system. In order to visualize the enhanced band valley degeneracy at elevated temperatures, the ground state eigenvalues and weights are projected by convolution functions that account for high temperature effects. Our results provide theoretical evidences for the role of sublattice strain in the band valley degeneracy observed in Mg2Si1-xSnx.

Original languageEnglish
Pages (from-to)939-946
Number of pages8
JournalPhysical Chemistry Chemical Physics
Volume18
Issue number2
DOIs
Publication statusPublished - 2015 Nov 27

Fingerprint

Conduction bands
valleys
conduction bands
sublattices
Solid solutions
High temperature effects
solid solutions
Seebeck coefficient
Tensile strain
Convolution
Ground state
Density functional theory
Seebeck effect
convolution integrals
temperature effects
eigenvalues
density functional theory
ground state
Temperature
temperature

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

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abstract = "To better understand the thermoelectric efficiency of the Mg-based thermoelectrics, using hybrid density-functional theory, we study the microscopic origins of valley degeneracies in the conduction band of the solid solution Mg2Si1-xSnx and its constituent components - namely, Mg2Si and Mg2Sn. In the solid solution of Mg2Si1-xSnx, the sublattices are expected to undergo either tensile or compressive strain in the light of Vegard's law. Interestingly, we find both tensile strain of Mg2Si and compressive strain of Mg2Sn enhance the conduction band valley degeneracy. We suggest that the optimal sublattice strain as one of the origins of the enhanced Seebeck coefficient in the Mg2Si1-xSnx system. In order to visualize the enhanced band valley degeneracy at elevated temperatures, the ground state eigenvalues and weights are projected by convolution functions that account for high temperature effects. Our results provide theoretical evidences for the role of sublattice strain in the band valley degeneracy observed in Mg2Si1-xSnx.",
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Unraveling the origins of conduction band valley degeneracies in Mg2Si1-xSnx thermoelectrics. / Kim, Chang Eun; Soon, Aloysius; Stampfl, Catherine.

In: Physical Chemistry Chemical Physics, Vol. 18, No. 2, 27.11.2015, p. 939-946.

Research output: Contribution to journalArticle

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AB - To better understand the thermoelectric efficiency of the Mg-based thermoelectrics, using hybrid density-functional theory, we study the microscopic origins of valley degeneracies in the conduction band of the solid solution Mg2Si1-xSnx and its constituent components - namely, Mg2Si and Mg2Sn. In the solid solution of Mg2Si1-xSnx, the sublattices are expected to undergo either tensile or compressive strain in the light of Vegard's law. Interestingly, we find both tensile strain of Mg2Si and compressive strain of Mg2Sn enhance the conduction band valley degeneracy. We suggest that the optimal sublattice strain as one of the origins of the enhanced Seebeck coefficient in the Mg2Si1-xSnx system. In order to visualize the enhanced band valley degeneracy at elevated temperatures, the ground state eigenvalues and weights are projected by convolution functions that account for high temperature effects. Our results provide theoretical evidences for the role of sublattice strain in the band valley degeneracy observed in Mg2Si1-xSnx.

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