Atomic-scale simulation of finite temperature thermodynamic properties of materials

Dnr:

SNIC 2018/3-184

Type:

SNAC Medium

Principal Investigator:

Malin Selleby

Affiliation:

Kungliga Tekniska högskolan

Start Date:

2018-04-27

End Date:

2019-05-01

Primary Classification:

20506: Metallurgy and Metallic Materials

Secondary Classification:

20502: Composite Science and Engineering

Tertiary Classification:

10304: Condensed Matter Physics

The CALPHAD method is a very powerful approach to fully describe the thermodynamic properties of different materials. 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. In addition, in some systems different experimental measurements may contradict among which selecting the reliable data is difficult. Ab-initio data can provide strong theoretical support for data selection in such cases.
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 and Mn [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 2017/1-140, 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. This work will continue application of mentioned DFT methods for calculating thermodynamic properties of hard materials, e.g. metallic carbides, at high temperatures.
[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).