title: Physics of bandgap formation in Cu-Sb-Se based novel thermoelectrics: the role of Sb valency and Cu d levels.
abstract: In this paper we discuss the results of ab initio electronic structure calculations for Cu(3)SbSe(4) (Se4) and Cu(3)SbSe(3) (Se3), two narrow bandgap semiconductors of thermoelectric interest. We find that Sb is trivalent in both the compounds, in contrast to a simple nominal valence (ionic) picture which suggests that Sb should be 5 + in Se4. The gap formation in Se4 is quite subtle, with hybridization between Sb 5s and the neighboring Se 4s, 4p orbitals, position of Cu d states, and non-local exchange interaction, each playing significant roles. Thermopower calculations show that Se4 is a better p-type system. Our theoretical results for Se4 agree very well with recent experimental results obtained by Skoug et al (2011 Sci. Adv. Mater. 3 602).
authors.affiliation: Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA. dodat@msu.edu
authors.forename: Dat
authors.initials: D
authors.lastname: Do
authors.forename: Vidvuds
authors.initials: V
authors.lastname: Ozolins
authors.forename: S D
authors.initials: SD
authors.lastname: Mahanti
authors.forename: Mal-Soon
authors.initials: MS
authors.lastname: Lee
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Zhang
authors.forename: C
authors.initials: C
authors.lastname: Wolverton