Ba8Cu16As30: A cationic-framework clathrate-I arsenide
Kaya Wei, Artem R. Khabibullin, Dean Hobbis, Winnie K. Wong-Ng, Tieyan Chang, SuYin G. Wang, Igor Levin, Yu-Sheng Chen, Lilia M. Woods, George S. Nolas
Single crystals of clathrate-I Ba8Cu16As30 have been synthesized, and their structure and electronic properties deter-mined using synchrotron-based X-ray diffraction and first principles calculations. The structure is confirmed to be cubic and defined by a tetrahedrally bonded network of As and Cu that forms two distinct coordination polyhedra, with Ba residing inside these polyhedra. All crystallographic positions are fully occupied with no vacancies or superstructure, and Cu atoms exhibit preference for the 6c site in the network. Agreement between the experimental and theoretically predicted structures was achieved after accounting for spin-orbit coupling. Our calculated Fermi surface, electron localization and charge transfer, as well as a comparison with the results for elemental As46, provide insight into the fundamental properties of this cationic- framework clathrate-I material.