Quasiharmonic Vibrational Properties of TiNiSn from Ab Initio Phonons

• Published in: Journal of electronic materials 2012-06, Vol.41 (6), p.977-983
• Main Authors: Wee, Daehyun, Kozinsky, Boris, Pavan, Barbara, Fornari, Marco
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Density; Electron states; Electronics and Microelectronics; Equations of state of specific substances; Equations of state, phase equilibria, and phase transitions; Estimates; Exact sciences and technology; Harmonic analysis; Heat conductivity; Heat transfer; Instrumentation; Lattice dynamics; Materials Science; Mathematical models; Methods of electronic structure calculations; Optical and Electronic Materials; Phonons; Phonons and vibrations in crystal lattices; Physics; Solid State Physics; Structure of solids and liquids; crystallography; Theory of crystal structure, crystal symmetry; calculations and modeling; Thermal conductivity; Thermal expansion; Thermodynamic properties; Thermodynamics; Vibration analysis
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-011-1833-4

We report an ab initio study of vibrational and thermodynamic properties of TiNiSn, a half-Heusler alloy that has been investigated in the context of thermoelectrics, based on density functional theory and density functional perturbation theory. The quasiharmonic approximation, where the Helmholtz free energy obtained from phonons of multiple strained structures is fitted to a model equation of state, is employed to estimate thermodynamic properties. Good quantitative correspondence is achieved between experimental observations and our theoretical calculation for various thermodynamic quantities: lattice parameter, thermal expansion coefficient, and heat capacity. Estimates of lattice thermal conductivity are also provided by using a semianalytic model previously proposed in the literature. Though this yields good qualitative agreement, a more accurate ab initio approach that explicitly includes anharmonic interactions between atoms should be employed for quantitative predictions of thermal conductivity.