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MM: Fachverband Metall- und Materialphysik

MM 10: Poster Session 1

MM 10.26: Poster

Montag, 5. September 2022, 18:00–20:00, P2

Ab initio study of point defects in disordered systems — •Pavel Papez¹, Martin Friák², and Martin Zelený¹ — ¹Institute of Materials Science and Engineering, Faculty of Mechanical Engineering, Brno University of Technology, Brno, Czech Republic — ²Institute of Physics of Materials, v.v.i., Czech Academy of Sciences, Brno, Czech Republic

This work is focused on a theoretical study of the influence of N and C interstitials in the equiatomic medium entropy alloy CoCrNi. These interstitials can be found in the alloy as contamination after preparation by powder-metallurgy techniques. The study was done by employing ab initio calculations based on the density functional theory and was performed by Vienna Ab initio Simulation Package (VASP) using the projector-augmented-wave formalism. The calculations were done on 6x6x2 supercells generated by using the special quasi-random structures approach (SQS) consisting of 216 atoms. The supercell consisted of 6 lattice planes {1 1 1} along the z-axis. The hcp structures were made from the fcc cells by moving the planes to create the hcp ABABAB stacking. Our results have shown which interstitial positions result in the lower enthalpy of formation. They are characterized by a higher amount of Cr and lower amount of Ni in their nearest neighbours (NN) shell with the most stable being the one with 2 Co, 3 Cr, and 1 Ni in its 1st NN shell. The stacking fault energy (SFE) was calculated using the first-order axial Ising model and by explicit stacking-fault calculations in two times larger fcc supercell. The results shown that interstitials always increase the SFE.