University of Birmingham > Talks@bham > School of Metallurgy and Materials Colloquia > Accurate high temperature properties of zirconium carbide from ab initio and multi-scale modelling of nickel-titanium and titanium

Accurate high temperature properties of zirconium carbide from ab initio and multi-scale modelling of nickel-titanium and titanium

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Density functional theory (DFT) is state of the art for a wide range of materials modelling applications, yet its application to model high temperature properties has proven challenging. The first half of this talk will focus on our TU-TILD method, which makes possible DFT -accurate free energies and accurate thermodynamic properties up to the melting point, within a computationally amenable framework. Results of calculations on zirconium carbide – a prototypical ultra-high temperature ceramic for which applications in extreme environments such as nuclear reactors and ultrasonic flight are being actively sought – will be presented, with the heat capacity, thermal expansion and elastic properties calculated up to the melting point. Furthermore the properties of vacancies and Frenkel defects in zirconium carbide and their effect on these thermodynamic properties will be fully explored.

In the second half of the talk I will focus on interatomic potentials, which play a crucial role in the modelling of materials where large length- or time-scales are necessary to capture the relevant phenomena or statistics. Here I will discuss the features and algorithms of the MEA Mfit code, which facilitates the optimization of LAMMPS -ready potentials, taking input direct from widely used DFT codes (VASP and CASTEP ). A recent application to explore the temperature—and strain-induced beta-gamma phase transformation in nickel titanium will be presented, and the role of point—and extended-defects on the characteristic transformation temperatures will be elucidated. Another recent application to titanium will also be presented in which the large length-scales accessible to potentials has made possible the prediction of new ‘linear-chain disordered’ variants of the titanium omega structure.

This talk is part of the School of Metallurgy and Materials Colloquia series.

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