From bonding asymmetry to anharmonic rattling in Cu12Sb4S13 tetrahedrites: When lone-pair electrons are not so lonely

Wei Lai, Yuxing Wang, Donald T. Morelli, Xu Lu

Research output: Contribution to journalArticle

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Abstract

Some of the best thermoelectrics are complex materials with rattling guests inside oversized atomic cages. Understanding the chemical and structural origins of the rattling behavior is essential to the design of thermoelectric materials. In this work, a clear connection is established between the local bonding asymmetry and anharmonic rattling modes in tetrahedrite thermoelectrics, enabled by the chemically active electron lone pairs. The studies reveal a five-atom atomic cage Sb[CuS3]Sb in Cu12Sb4S13 tetrahedrites that exhibits strong local bonding asymmetry: covalent bonding inside the CuS3 trigonal plane and weak out-of-plane bonding induced by the lone-pair electrons of Sb. This bonding asymmetry leads to out-of-plane rattling modes that are quasilocalized and anharmonic with low frequency and large amplitude, and are likely the origin of low thermal conductivity in tetrahedrites. Such knowledge highlights the importance of local structure asymmetry and lone-pair atoms in driving anharmonic rattling, providing a stepping stone to the discovery and design of next-generation thermoelectrics. A strong local bonding asymmetry is identified inside a Sb[CuS3]Sb atomic cage, in which Cu (blue) forms strong covalent bonding with S (green and yellow) and forms weak covalent bonding with one of the Sb atoms (brown) enabled by the lone-pair electrons. This bonding asymmetry causes the out-of-plane anharmonic rattling which leads to the low thermal conductivity.

LanguageEnglish (US)
Pages3648-3657
Number of pages10
JournalAdvanced Functional Materials
Volume25
Issue number24
DOIs
StatePublished - Jun 1 2015

Profile

asymmetry
Electrons
electrons
Atoms
Thermal conductivity
thermal conductivity
atoms
cupric sulfide
thermoelectric materials
low frequencies
causes

Keywords

  • anharmonic rattling
  • bonding asymmetry
  • lone-pair electrons
  • tetrahedrite
  • thermoelectrics

ASJC Scopus subject areas

  • Biomaterials
  • Electrochemistry
  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

From bonding asymmetry to anharmonic rattling in Cu12Sb4S13 tetrahedrites : When lone-pair electrons are not so lonely. / Lai, Wei; Wang, Yuxing; Morelli, Donald T.; Lu, Xu.

In: Advanced Functional Materials, Vol. 25, No. 24, 01.06.2015, p. 3648-3657.

Research output: Contribution to journalArticle

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