Synchrotron-Radiation Infrared Microspectroscopy of Marcasite-Type NiN2

The electronic structure of the marcasite-type NiN2, newly synthesized under high pressures and high temperatures, was investigated using synchrotron-radiation infrared (IR) microspectroscopy and first-principles calculations based on the density functional theory (DFT). The IR spectrum of the marca...

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Bibliographic Details
Published in:Journal of the Physical Society of Japan 2022-04, Vol.91 (4), p.044702
Main Authors: Soda, Kazuo, Kawada, Takuya, Niwa, Ken, Hasegawa, Masashi, Ikemoto, Yuka
Format: Article
Language:English
Subjects:
Carrier density
Conduction bands
Density functional theory
Electronic structure
First principles
High temperature
Infrared radiation
Lattice vibration
Radiation
Synchrotrons
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Summary:The electronic structure of the marcasite-type NiN2, newly synthesized under high pressures and high temperatures, was investigated using synchrotron-radiation infrared (IR) microspectroscopy and first-principles calculations based on the density functional theory (DFT). The IR spectrum of the marcasite-type NiN2 showed characteristic low reflectance of the semiconductor with spectral features probably due to defects or lattice vibrations and free carriers. The effective free-carrier concentration in the marcasite-type NiN2 was estimated by fitting a Drude–Lorentz model for the optical response to be 1024–25 m−3, much less than those of normal metals (1028–29 m−3) and comparable to the estimated concentration of the thermally-excited carrier in the conduction band. The DFT predictions could semi-quantitatively explain the experimental findings; at 36 GPa, the marcasite-type NiN2 had a narrow gap between the Ni 3d aσ bands split in the distorted octahedral coordination of N neighbors.
ISSN:0031-9015
1347-4073
DOI:10.7566/JPSJ.91.044702