Critical evaluation of calculated molar volumes for Al ? Ni phases

S. TUMMINELLO; M. PALUMBO; J. KOSSMANN; T. HAMMERSCHMIDT; R. DRAUTZ; S. SOMMADOSSI; P. R. ALONSO; N. DUPIN; S.G. FRIES

Santos

Congreso; TOFA 2016- Discussion meeting on thermodynamics of alloys; 2016

CRITICAL EVALUATION OF CALCULATED MOLAR VOLUMES FOR AL-NI PHASESTumminello, S.(1); Palumbo, M.(2); Kossmann, J.(2); Hammerschmidt, T.(2); Drautz, R.(2); Sommadossi, S.(3); Alonso, P.R.(4); Dupin, N.(5); Fries, S.G.(2);(1) UNCo-UNSAM; (2) RUB; (3) UNCo- CONICET; (4) UNSAM-CNEA; (5) CT;Keyword: DFT, CEF, multiphase stability, first-principlesAbstract:Molar volumes for all the phases in a multiphase equilibria environment like CALPHAD are desirable to calculate for example, volume changes in phase transformations or volume fractions of stable phases. Electronic-structure calculations based on density functional theory allow to calculate volumes for stable and also for metastable phases and hypothetical compounds, and can be extended to finite temperatures including vibrations. In this work molar volumes for ordered compounds used to model the fcc bcc and hcp solutionphases, and topologically closed packed phases for the binary Al-Ni were obtained using DFT within the GGA approximation. Moreover, phonon calculations with the harmonic and quasiharmonic approximations for pure Al and pure Ni including electronic contributions were performed and the molar volume as afunction of temperature was obtained obtained from the quasiharmonic results. We compare our results with experimental, e.g Ellner et al. [1], and theoretical volumes found in literature. We also evaluate the possibility of including calculated volumes in an entirely first-principles thermodynamic database format.[1] M. Ellner, U. Kattner and B. J. Predel, J. Less-Common Met 87 (1982) 305-325.