Hydrogen–vacancy interactions in ferromagnetic and paramagnetic bcc iron: Ab initio calculations

Abstract

Simulation of the paramagnetic state is still a challenge for computer material science. At the same time, for iron alloys the region of the paramagnetic state is important from the viewpoint of processing. The paper presents results of ab initio modeling of interaction of hydrogen atom with a vacancy in both ferromagnetic and (for the first time) paramagnetic bcc iron. The interaction energy calculations are carried out in the framework of the local spin density approximation (LSDA) by using the supercell LAPW‐WIEN‐2k method. To obtain the disordered distribution of magnetic moments the program package BINAR was used. Fifteen nonequivalent magnetic configurations were obtained. Five of them having the lowest energy were chosen for further analysis. The H–O site distance is 0.23 Å in both paramagnetic and ferromagnetic bcc iron. The energy of hydrogen trapping by the vacancy is 0.60 and 0.27 for paramagnetic and ferromagnetic state, respectively. It is found that weakening of the H–V interaction in the paramagnetic state is the consequence of magnetic effects.