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First‐principles study of the pressure‐induced α → ω transition in titanium
Author(s) -
Jona F.,
Marcus P. M.
Publication year - 2005
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200540110
Subject(s) - gibbs free energy , phase transition , thermodynamics , maxima and minima , zero point energy , chemistry , zero (linguistics) , phase (matter) , lattice (music) , condensed matter physics , zero temperature , energy (signal processing) , physics , quantum mechanics , mathematics , mathematical analysis , linguistics , philosophy , organic chemistry , acoustics
The pressure‐induced transition from the α to the ω ‐phase of Ti is studied with first‐principles total‐energy calculations by a procedure that finds the equilibrium structures of each phase directly as a function of pressure from minima of the Gibbs free energy. Good to excellent agreement with experiment is found for the lattice parameters of the two phases both at zero pressure and as functions of pressure up to 900 kbar. The Gibbs free energies of the two phases at zero temperature and without zero‐point energy cross at about 500 kbar and then again at 700 kbar. Below 500 and above 700 kbar the α ‐phase has the lower free energy. Thus, unlike previous theoretical treatments, but in agreement with experiment, our procedure finds the α ‐phase more stable than the ω ‐phase below 500 kbar. The α → ω transition pressure of 500 kbar is much higher than observed experimentally. Possible reasons for this discrepancy, as well as for the non‐observance of the re‐entrant α ‐phase above 700 kbar are presented. The importance of the zero‐point energy in determining the ground‐state phase and transition pressure is noted. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)