Title:	Atomic-scale simulation of finite temperature thermodynamic properties of materials
DNr:	SNIC 2017/1-140
Project Type:	SNIC Medium Compute
Principal Investigator:	Malin Selleby <malin@kth.se>
Affiliation:	Kungliga Tekniska högskolan
Duration:	2017-04-01 – 2018-04-01
Classification:	20506 20502 10304
Homepage:	http://www.hero-m.mse.kth.se/page.php?pid=184
Keywords:

Abstract

The CALPHAD method is a very powerful approach to fully describe the thermodynamic properties of different materials based on limited available data. In this method, model parameters are fitted to experimental data to develop databases which may then easily be used by industry or academia for material design and property prediction. In the absence of experimental data due to difficulty in measurements or metastable systems, the ab-initio methods are helpful tools to calculate and provide thermodynamic properties required for CALPHAD modelling. Since the main interest in metallurgical processes is focused on phase transformations occurring at high temperatures, the DFT methods that just provide data at 0 K are of limited use in CALPHAD modelling. On the other hand, the methods that provide thermodynamic data up to the melting point can provide a significant help in filling the gap of missing data. Recent advances in highly efficient computational schemes have enabled the calculation of thermodynamic properties, including the anharmonic contribution to both free energy and heat capacity, up to the melting point for many pure elements [1,2]. The UP-TILD method [1] was shown to give reliable results for Al [1], Cu [3] and Ag [4], and even for magnetic elements such as Cr [5]. 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 [2]. The aim of this project is to model the different contributions (magnetic, electronic, harmonic, anharmonic) to the free energy of the materials by using DFT data, and thermodynamic integration going from a classical MD reference states to ab initio molecular dynamics. Modelling thermodynamic properties of materials by DFT methods is a good way to combine the first principle methods and CALPHAD modelling as a promising approach for practical use of basic physics in engineering. This project is a continuation of project SNIC 2016/1-117, in which new DFT methods have been used for calculating the finite temperature thermodynamic properties of different elements, e.g. Co, Mn, Ni and Te, and the results are so far so promising. However, there is still some discrepancy with the experimental data and we are quite confident that repeating calculations with larger size supercell will improve the results. The aim of current project is to continue these calculations until getting a satisfactory agreement with the experimental data. [1] B. Grabowski, L. Ismer, T. Hickel and J. Neugebauer, Phys. Rev. B 79 (13), 134106 (2009). [2] A. I. Duff, T. Davey, D. Korbmacher, A. Glensk, B. Grabowski, J. Neugebauer and M. W. Finnis, Phys. Rev. B 91 (21), 214311 (2015). [3] A. Glensk, B. Grabowski, T. Hickel and J. Neugebauer, Phys. Rev. X 4 (1), 011018 (2014). [4] A. Glensk, B. Grabowski, T. Hickel and J. Neugebauer, Phys. Rev. Lett. 114 (19), 195901 (2015). [5] F. Körmann, B. Grabowski, P. Söderlind, M. Palumbo, S. G. Fries, T. Hickel and J. Neugebauer, J. Phys.: Condens. Matter 25 (42), 425401 (2013).