Dynamical Bond Formation in KNi2Se2

James Neilson (1) , Allyson Fry-Petit (1, 2) , Natalia Drichko (1) , Matthew Stone (3) , Anna Llobet (4) , Mahalingam Balasubramanian (5) , Matthew R. Suchomel (6, 5) , Tyrel Mcqueen (1, 7)

1 Institute for Quantum Matter
2 Department of Chemistry
3 ORNL - Oak Ridge National Laboratory [Oak Ridge]
4 Lujan Center for Neutron Scattering, LANL
5 APS - Advanced Photon Source [ANL]
6 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
7 Department of Materials Science and Engineering

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 zigzag 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.

Domaines: Matériaux

James Neilson, Allyson Fry-Petit, Natalia Drichko, Matthew Stone, Anna Llobet, et al.. Dynamical Bond Formation in KNi2Se2. Journal of Inorganic and General Chemistry / Zeitschrift für anorganische und allgemeine Chemie, 2022, 648 (15), e202200042 (7 p.). ⟨10.1002/zaac.202200042⟩. ⟨hal-03677240⟩