Mixing and decomposition thermodynamics of c-Ti1-xAlxN from first-principles calculations
2007 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 045123Article in journal (Refereed) Published
Wedescribe an efficient first-principles method that can be used tocalculate mixing enthalpies of transition metal nitrides with B1 structureand substitutional disorder at the metal sublattice. The technique isbased on the density functional theory. The independent sublattice modelis suggested for the treatment of disorder-induced local lattice relaxationeffects. It supplements the description of the substitutional disorder withinthe coherent potential approximation. We demonstrate the excellent accuracy ofthe method by comparison with calculations performed by means ofthe projector augumented wave method on supercells constructed as specialquasirandom structures. At the same time, the efficiency of thetechnique allows for total energy calculations on a very finemesh of concentrations which enables a reliable calculation of thesecond concentration derivative of the alloy total energy. This isa first step towards first-principles predictions of concentrations and temperatureintervals where the alloy decomposition proceeds via the spinodal mechanism.We thus calculate electronic structure, lattice parameter, and mixing enthalpiesof the quasibinary alloy c-Ti1−xAlxN. The lattice parameter follows Vegard'slaw at low fractions of AlN but deviates increasingly withincreasing Al content. We show that the asymmetry of themixing enthalpy and its second concentration derivative is associated withsubstantial variations of the electronic structure with alloy composition. Thephase diagram is constructed within the mean-field approximation.
Place, publisher, year, edition, pages
2007. Vol. 75, no 045123
titanium compounds, aluminium compounds, III-V semiconductors, wide band gap semiconductors, mixing, spinodal decomposition, enthalpy, heat of mixing, ab initio calculations, density functional theory, CPA calculations, total energy, electronic structure, lattice constants, phase diagrams
IdentifiersURN: urn:nbn:se:liu:diva-38399DOI: 10.1103/PhysRevB.75.045123Local ID: 44185OAI: oai:DiVA.org:liu-38399DiVA: diva2:259248
Björn Alling, A. V. Ruban, A. Karimi, O. E. Peil, Sergey Simak, Lars Hultman and Igor Abrikosov, Mixing and decomposition thermodynamics of c-Ti1-xAlxN from first-principles calculations, 2007, Physical Review B. Condensed Matter and Materials Physics, (75), 045123.
Copyright: American Physical Society