Structural, electronic properties and inter-atomic bonding in layered chalcogenide oxides LaMChO (where M = Cu, Ag, and Ch = S, Se) from FLAPW-GGA calculations

• Published in: Solid state sciences 2012, Vol.14 (1), p.89-93
• Main Authors: BANNIKOV, V. V, SHEIN, I. R, IVANOVSKII, A. L
• Format: Article
• Language: English
• Subjects: Anisotropy; Bonding; Chalcogenides; Chemical bonds; Copper; Electronic properties; Oxides; Silver
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2011.10.022

Using the first principles FLAPW-GGA method, comparative study of structural, electronic properties and of chemical bonding in four 1111-like chalcogenide oxides LaMChO (LaCuSO, LaCuSeO, LaAgSO, and LaAgSeO) with ZrCuSiAs-type structure was performed. Our studies showed that: (i) replacements of dmetal atoms (Cu a" Ag) and chalcogen atoms (S a" Se) lead to anisotropic deformations of the crystal structure; this effect is related to strong anisotropy of inter-atomic bonds; (ii) all of the examined chalcogenide oxides are semiconducting; the band gap decreases both at S a' Se and Cu a' Ag substitutions; and (iii) the bonding in LaMChO phases can be classified as a high-anisotropic mixture of ionic and covalent contributions, where mixed covalent-ionic bonds take place inside [La2O2] and [M2|>Ch2] blocks, whereas between the adjacent [La2O2]/[M|>2|>Ch|>2] blocks, ionic bonds emerge owing to [La2O2] a' [M2|>Ch|>2] charge transfer. Since the near-Fermi bands of LaMChO phases originate mainly from electronic states of [M2Ch|>2] blocks, we speculate that chemical substitutions inside these blocks can result in striking differences in electronic properties of these systems; therefore, this approach can be promising for significant enlargement of the functional properties of these materials.