Abstract
The solid solution BaCo1-xNixS2 exhibits an insulator-to-metal transition close to x=0.21. Questions of whether this transition is coupled with structural changes remain open. Here we follow the structural evolution as a function of the Ni content x using synchrotron powder x-ray diffraction and pair distribution function analyses to reveal significant basal sulfide anion displacements occurring preferentially along the CoS5 pyramidal edges comprising the edge-connected bond network in BaCo1-xNixS2. These displacements decrease in magnitude as x increases and are nearly quenched in x=1BaNiS2. Density-functional-theory-based electronic structure calculations on x=0BaCoS2 suggest that these displacements arise as a dynamic first-order Jahn-Teller effect owing to partial occupancy of nominally degenerate Co2+dxz and dyz orbitals, leading to local structural symmetry breaking in the xy-plane of the Co-rich phases. The Jahn-Teller instability is associated with the opening of a band gap that is further strengthened by electronic correlation. The Jahn-Teller effect is reduced upon increased electron filling as x→1, indicating that the local structure and band filling cooperatively result in the observed insulator-to-metal transition.
| Original language | English (US) |
|---|---|
| Article number | 104401 |
| Journal | Physical Review Materials |
| Volume | 4 |
| Issue number | 10 |
| DOIs | |
| State | Published - Oct 1 2020 |
Funding
This research was supported by the National Science Foundation under DMREF Awards No. DMR-1729489 and No. DMR-1729303. Use of the Shared Experimental Facilities of the Materials Research Science and Engineering Center (MRSEC) at UC Santa Barbara (DMR 1720256) is gratefully acknowledged. The UC Santa Barbara MRSEC is a member of the NSF-supported Materials Research Facilities Network . We also acknowledge support from the Center for Scientific Computing from the CNSI, MRL: an NSF MRSEC (DMR-1720256) and NSF CNS-1725797. This research was also supported, in part, through the computational resources and staff contributions provided for the Quest high performance computing facility at Northwestern University which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern University Information Technology. Additionally, this research used the Extreme Science and Engineering Discovery Environment (XSEDE) Stampede2, which is supported by National Science Foundation Grant Number ACI-1548562 and hosted by the Texas Advanced Computing Center (TACC) at the University of Texas at Austin. Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
ASJC Scopus subject areas
- General Materials Science
- Physics and Astronomy (miscellaneous)