Origin of direct band gap of Li2CN2 studied by first-principle calculations

• Published in: Physica. B, Condensed matter Vol. 598; p. 412442
• Main Authors: Kushida, Kazumasa, Kuriyama, Kazuo
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.12.2020; Elsevier BV
• Subjects: Band gap; Band structure; Band structure modification; Computer simulations; Conduction bands; Covalent bonds; Electronic band structure; Electronic structure; Energy gap; First principles; Inorganic materials; Lithium ions; Luminescence; Mathematical analysis; Studies; Tetragonal lattice; Valence band; Band structure modification; Computer simulations; Inorganic materials; Electronic band structure
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2020.412442

Origin of the direct band gap of Li2CN2 is studied by first-principle calculations. For this purpose, electronic structure of Li2CN2 is compared with that of a hypothetical body centered tetragonal [CN2]2- lattice equivalent to Li2CN2 in the number of valence electrons. Li2CN2 can be viewed as [CN2]2- lattice whose distorted tetrahedral sites are occupied by Li+ ions. [CN2]2- lattice shows an indirect band gap between the Z point as the valence band maximum and the Γ point as the conduction band minimum. The occupation of the distorted tetrahedral sites in [CN2]2- lattice by Li+ causes the formation of covalent bonds between Li and N, resulting in a large downward shift in the energy position of the Z point of the conduction band. As the result, the Z point is exposed as the conduction band minimum, which is the origin of the direct band gap in Li2CN2.