Abstract
Emphanisis, or the appearance out of nothing, has been used to describe the phenomena of spontaneous atom off-centering and dipole formation at elevated temperatures in lead chalcogenides. Here, we provide spectroscopic evidence of spontaneous formation of metal-metal bonds above T∼50 K in the layered metal KNi2Se2. These bonds form zig-zag chains that lower the local symmetry from tetragonal to monoclinic. Energy-resolved pair distribution function measurements exclude a pure phonon origin of our observations, and instead imply the existence of extra, slowly fluctuating, Ni−Ni bonds above T=50 K. Density functional theory calculations support this lower symmetry configuration as an instability of tetragonal KNi2Se2. We thus demonstrate that the phenomena of emphansis is not limited to local electric dipole formation, but can also be driven by the formation of metal-metal bonds.
| Original language | English |
|---|---|
| Article number | e202200042 |
| Journal | Zeitschrift fur Anorganische und Allgemeine Chemie |
| Volume | 648 |
| Issue number | 15 |
| DOIs | |
| State | Published - Aug 12 2022 |
Funding
We thank James Murray and Zlatko Tesanovic for inspiration and motivation, Igor Mazin for helpful discussions, Kevin Bayer and Karena Chapman for data collection at 11‐ID−B, and Collin Broholm, Martin Mourigal, and W. Adam Phelan for help with the ARCS experiments. We thank W. Dmowski and T. Egami for use of their annular vanadium can. This research and the Raman spectrometer were supported by the US Department of Energy (DoE), Office of Science, Office of Basic Energy Sciences (BES), Division of Materials Sciences and Engineering under award DE‐FG02‐08ER46544. TMM acknowledges support from the David and Lucile Packard Foundation. This research has benefited from the use of beamlines 11‐BM‐B, 11‐ID‐B, and 20‐BM‐B at the Advanced Photon Source at Argonne National Laboratory, supported by the US. DoE, Office of Science, Office of Basic Energy Sciences, under Contract No. DE‐AC02‐06CH11357. Some initial work was performed at the Lujan Center at the Los Alamos Neutron Science Center, funded by the Office of Basic Energy Sciences of the US DoE. The Los Alamos National Laboratory was operated by Los Alamos National Security LLC under DOE contract DE‐AC52‐06NA25396. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. We thank James Murray and Zlatko Tesanovic for inspiration and motivation, Igor Mazin for helpful discussions, Kevin Bayer and Karena Chapman for data collection at 11-ID−B, and Collin Broholm, Martin Mourigal, and W. Adam Phelan for help with the ARCS experiments. We thank W. Dmowski and T. Egami for use of their annular vanadium can. This research and the Raman spectrometer were supported by the US Department of Energy (DoE), Office of Science, Office of Basic Energy Sciences (BES), Division of Materials Sciences and Engineering under award DE-FG02-08ER46544. TMM acknowledges support from the David and Lucile Packard Foundation. This research has benefited from the use of beamlines 11-BM-B, 11-ID-B, and 20-BM-B at the Advanced Photon Source at Argonne National Laboratory, supported by the US. DoE, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Some initial work was performed at the Lujan Center at the Los Alamos Neutron Science Center, funded by the Office of Basic Energy Sciences of the US DoE. The Los Alamos National Laboratory was operated by Los Alamos National Security LLC under DOE contract DE-AC52-06NA25396. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.
Keywords
- diffraction
- emphansis
- metal-metal bonding
- pair distribution function
- raman scattering