SNIC
SUPR
SNIC SUPR
Atomic-scale simulation of diffusion and nucleation processes in liquid and liquid-solid interfaces
Dnr:

SNIC 2018/3-417

Type:

SNAC Medium

Principal Investigator:

Carlos Moyses Graca Araujo

Affiliation:

Uppsala universitet

Start Date:

2018-09-01

End Date:

2019-03-01

Primary Classification:

10304: Condensed Matter Physics

Webpage:

Allocation

Abstract

The project is focused on the investigation of liquid phase diffusion and crystal growth mechanisms [1] in energy interesting materials. The microstructural evolution during sintering of hard metals and steels is an important way to control their mechanical properties. It is difficult to experimentally determine elemental mobilities in a liquid at high temperatures. Our study aims at achieving fundamental understanding of liquid and solid-liquid interface dynamics starting from atomic scale simulations. More specifically our research activities will be oriented to study the diffusion of dissolved elements in a liquid, the effect of clustering of such elements in the liquid environment as well as the nucleation of new crystal layers on the solid-liquid interfaces. The latter is actually the ultimate goal of this project where we will be developing methodology to simulate realistic conditions on the crystal growth processes. We will use state of the art first-principles methods based on quantum and statistical mechanics, viz. density functional theory (DFT), molecular dynamics (MD) and Kinetic Monte Carlo simulations. MD simulations are well suited for simulating fast processes like diffusion in liquids. However, processes with higher energy barriers, like nucleation of new crystal layers, can be treated in a much more efficient way by the use of Kinetic Monte Carlo [2, 3]. The electronic structure at finite temperature will be evaluated by using ab initio MD simulations. Here, a sequential MD/DTF scheme will be used where some snapshots of the simulation are chosen to carry out high-accurate single point DFT calculations, and then, the obtained electronic structures are averaged. The aim is to develop a methodology that allows for direct comparison with in-situ spectroscopy measurements. Such combined experiment-theory approach can be very efficient to unveil the underlying physics at atomic scale [4]. Besides that, the simulations will also be used to evaluate the free energy of different pathways of the nucleation process. More specifically we are interested in the growth process of cemented carbides that will be connected with organic materials to form hybrid electrodes. Therefore, we are going to study the liquids of elemental Co, Fe and Ni with commonly dissolved elements like C, W, Ti, Ta, Nb, V, Cr. The solid particles in the solid-liquid interface will start with WC and then growing new layers. The knowledge gained from this project will be relevant for the steel industry in general. References: [1] R. Valiullin et al. Nature 433, 965 (2006). [2] L. Xu and G. Henkelman J. Chem. Phys. 129, 114104 (2008). [3] G. Henkelman, and H. Jónsson J. Chem. Phys. 115, 9657 (2001). [4] A. Hirata et al. Nature Mat. 10, 28 (2011).