First-principles investigation of the electronic and lattice vibrational properties of Mg2C

• Published in: Computational materials science Vol. 93; pp. 234 - 238
• Main Authors: Li, Tongwei, Ju, Weiwei, Liu, Huihui, Cui, Hongling, Zhao, Xiaoyan, Yong, Yongliang, Feng, Zhenjie
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2014; Elsevier
• Subjects: Carbides; Condensed matter: structure, mechanical and thermal properties; Density-functional calculation; Electronics; Exact sciences and technology; High-pressure and shock-wave effects in solids and liquids; Infrared; Infrared and Raman spectra; Lattice dynamics; Lattice vibration; Lattices; Magnesium; Mathematical analysis; Mechanical and acoustical properties of condensed matter; Phonon states and bands, normal modes, and phonon dispersion; Phonons and vibrations in crystal lattices; Physics; Semiconductors; Splitting; Infrared and Raman spectra; Density-functional calculation; Carbides; Raman spectra; Pressure effects; Dielectric tensor; Infrared spectra; Electronic density of states; Magnesium carbide; High pressure; Optical phonons; Narrow band gap semiconductors; Phonon mode; Vibrational modes; Density functional method
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2014.06.048

[Display omitted] •The electronic band gap of Mg2C decreases slowly with pressure increasing.•There are two optical vibrational modes at the Γ point (F1u and F2g).•Their vibrational frequencies increase sharply with pressure increasing.•The optical modes at Γ point have large infrared intensity and Raman activity.•Large LO–TO splitting is found in the F1u mode of Mg2C. Mg2C, a newly synthesized magnesium carbide under high pressure, is a small band gap semiconductor. A first-principles investigation of the electronic and lattice dynamic properties of Mg2C are presented. We find the electronic band gap of Mg2C decreases slowly with pressure increasing. There are two optical vibrational modes at the Γ point of Mg2C. One is F1u mode, and the other is F2g mode. The former mode is infrared active and the latter one is Raman active. Their vibrational frequencies increase sharply with pressure increasing. Furthermore, we find that Mg2C has large infrared intensity and Raman activity, which indicates that infrared and Raman spectra may play a key role in identifying Mg2C. Moreover, we calculate the dielectric tensor and LO–TO splitting under different pressure and find large LO–TO splitting in the F1u mode of Mg2C. Our calculated results provide extraordinary insights into the infrared and Raman spectra of Mg2C.