3rd generation of Calphad databases – ongoing work at KTH, Sweden
Friday, February 24, 2017
11:00 AM - 12:00 PM
Location: Steele 125
Sedi Bigdeli, Division of Computational Thermodynamics , Royal Institute of Technology (KTH), Stockholm, Sweden
In developing a new generation of Calphad databases, new models are used in which each term contributing to the Gibbs energy has a physical meaning. For example, harmonic vibrations of atoms are modelled using the Einstein temperature, anharmonic vibrations, electronic and magnetic contributions for solid phases, each have specific terms and the two-state model  is used for modelling the liquid phase. These models have already been used to describe the thermodynamic properties of a few unaries Fe , Mn , Cr , Ni , Co , Al and C  have been proven to work properly.
To be able to develop these new thermodynamic databases we are confined to use existing computational tools but at the same time we want to make the best possible use of atomistic methods . These methods have so far not been straightforward to use and have not been reliable at finite temperatures. Recently, however, new methods have been developed [9,10] for which the calculated thermodynamic properties at finite temperatures are much more accurate, the calculations being time efficient, and convenient. The UP-TILD method  was shown to give reliable results for Al , Cu  and Ag , and even for magnetic elements such as Cr . The TU-TILD method, which provides even better computational efficiency, has been shown to well describe the thermodynamics of ZrC, an ultrahigh-temperature ceramic compound . In the present work we use the TU-TILD method to model the thermodynamic properties of paramagnetic bcc Mn. Another alternative for DFT finite temperature calculations is the EMTO method [14-16] with the possibility to treat alloying disorder or paramagnetism using the coherent potential approximation CPA . In this project, EMTO-CPA is used for predicting magnetic ground state of hcp Mn and Fe. Using these new unary descriptions the work within Hero-m continues to describe the binaries and ternaries.
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Series: Special Seminar in Applied Physics and Materials Science
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