Structure family and polymorphous phase transition in the compounds with soft sublattice: Cu{sub 2}Se as an example

Journal Article · Sat May 21 04:00:00 EDT 2016 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4948609· OSTI ID:22658016

Qiu, Wujie ^[1]; Lu, Ping; Yuan, Xun; Liu, Huili; Shi, Xun; Chen, Lidong ^[2]; Xu, Fangfang; Wu, Lihua ^[2]; Ke, Xuezhi ^[1]; Yang, Jiong ^[3]; Yang, Jihui ^[4]; Zhang, Wenqing ^[2]

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1. Department of Physics, East China Normal University, Shanghai 200241 (China)
2. State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)
3. Materials Genome Institute, Shanghai University, Shanghai 200444 (China)
4. Materials Science and Engineering Department, University of Washington, Seattle, Washington 98195 (United States)

Quite a few interesting but controversial phenomena, such as simple chemical composition but complex structures, well-defined high-temperature cubic structure but intriguing phase transition, coexist in Cu{sub 2}Se, originating from the relatively rigid Se framework and “soft” Cu sublattice. However, the electrical transport properties are almost uninfluenced by such complex substructures, which make Cu{sub 2}Se a promising high-performance thermoelectric compound with extremely low thermal conductivity and good power factor. Our work reveals that the crystal structure of Cu{sub 2}Se at the temperature below the phase-transition point (∼400 K) should have a group of candidate structures that all contain a Se-dominated face-centered-cubic-like layered framework but nearly random site occupancy of atoms from the “soft” Cu sublattice. The energy differences among those structures are very low, implying the coexistence of various structures and thus an intrinsic structure complexity with a Se-based framework. Detailed analyses indicate that observed structures should be a random stacking of those representative structure units. The transition energy barriers between each two of those structures are estimated to be zero, leading to a polymorphous phase transition of Cu{sub 2}Se at increasing temperature. Those are all consistent with experimental observations.

• OSTI ID: 22658016
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 19 Vol. 144; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CHEMICAL COMPOSITION
COPPER SELENIDES
EXPERIMENTAL DATA
FCC LATTICES
PHASE TRANSFORMATIONS
POWER FACTOR
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
THERMAL CONDUCTIVITY