Electronic structure and point defect concentrations of C11b MoSi2 by first-principles calculations

• Published in: Journal of alloys and compounds Vol. 605; pp. 45 - 50
• Main Authors: Li, X.P., Sun, S.P., Wang, H.J., Lei, W.N., Jiang, Y., Yi, D.Q.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 25.08.2014; Elsevier
• Subjects: C11b MoSi2; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Defects and impurities in crystals; microstructure; Electron density of states and band structure of crystalline solids; Electron states; Electronic structure; Exact sciences and technology; First-principles calculation; Formation enthalpy; Physics; Point defects; Point defects (vacancies, interstitials, color centers, etc.) and defect clusters; Semiconductor compounds; Structure of solids and liquids; crystallography; Wagner–Schottky model; C11b MoSi2; Electronic structure; First-principles calculation; Point defects; Formation enthalpy; Wagner–Schottky model; Defect density; C11; Hybridization; Covalent bonds; Fracture toughness; Charge density; Vacancy density; Sublattices; Density functional method; Wagner―Schottky model; Molybdenum silicide; MoSi
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2014.03.159

•The point defects of C11b MoSi2 were studied systematically.•MoSi2 is semimetallic with strong directional covalent bonds.•Some rules of the point defect concentrations were revealed.•Vacancy is a main type of point defect in MoSi2. The electronic structure and point defect concentrations of C11b MoSi2 were studied systematically by the first-principles calculations based on density functional theory. Mo vacancy-induced charge density shows strong directional covalent bonds caused by hybridization of Mo-4d and Si-3p orbitals, which indicates that MoSi2 has low fracture toughness at room temperature. Combining with Wagner–Schottky model, these point defect concentrations of C11b MoSi2 at 2173, 1673, 1223, 773K as function of composition were also investigated. It is found that the point defect concentrations change drastically for off-stoichiometric compounds. The main structural defects are preferably Mo vacancies or Si anti-structure atoms on the Mo sublattices in Si-rich alloy, and Mo anti-site in Mo-rich alloy, respectively. According to the calculated effective formation enthalpies of point defects, the effective formation enthalpies from big to small in sequence are Mo anti-site, Si anti-site and vacancy (Mo and Si). This result suggests that the vacancy, especially for Si vacancy, is a main type of point defect in C11b MoSi2 system.