TY - JOUR A1 - Sözen, H.I. A1 - Mendive-Tapia, E. A1 - Hickel, Tilmann A1 - Neugebauer, J. T1 - Ab initio investigations of point and complex defect structures in B2-FeAl JF - Physical review materials N2 - We study single-site and two-site defect structures in B2-type Fe-Al alloys by means of density functional theory supercell calculations. The defect formation energies are calculated as functions of the chemical potential, which are used to obtain the dependence of the defect concentrations on Al content at different temperatures. We also examine the converging behavior of the formation energies with respect to the supercell size to study the corresponding limit of dilute defects. The effect of magnetism is investigated by considering nonmagnetic, ferromagnetic, and paramagnetic states, calculations for the latter showing that the magnitude of the local magnetic moments strongly impacts the defect formation energies. The methodological studies are used to provide explanations for the wide spread of defect formation energies reported by experiments and other theoretical investigations. Based on these insights, the stability of the B2-FeAl structure as a function of Al concentration is obtained and discussed. KW - Atomistic models KW - Defects KW - Thermodynamics PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-546956 DO - https://doi.org/10.1103/PhysRevMaterials.6.023603 SN - 2475-9953 VL - 6 IS - 2 SP - 1 EP - 11 PB - APS CY - College Park, MD AN - OPUS4-54695 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mendive-Tapia, E. A1 - Neugebauer, J. A1 - Hickel, Tilmann T1 - Ab initio calculation of the magnetic Gibbs free energy of materials using magnetically constrained supercells JF - Physical review B N2 - We present a first-principles approach for the computation of the magnetic Gibbs free energy ofmaterials using magnetically constrained supercell calculations. Our approach is based on an adiabatic approximation of slowly varying local moment orientations, the so-called finite-temperature disordered local moment picture. It describes magnetic phase transitions and how electronic and/or magnetostructural mechanisms generate a discontinuous (first-order) character. We demonstrate that the statistical mechanics of the local moment orientations can be described by an affordable number of supercell calculations containing noncollinear magnetic configurations. The applicability of our approach is illustrated by firstly studying the ferromagnetic state in bcc Fe. We then investigate the temperature-dependent properties of a triangular antiferromagnetic state stabilizing in two antiperovskite systems Mn3AN (A = Ga, Ni). Our calculations provide the negative thermal expansion of These materials as well as the ab initio origin of the discontinuous character of the phase transitions, electronic and/or magnetostructural, in good agreement with experiment. KW - Ab initio KW - Thermodynamics KW - Magnetic alloys KW - Phase transformations PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543710 DO - https://doi.org/10.1103/PhysRevB.105.064425 SN - 2469-9969 VL - 105 IS - 6 SP - 1 EP - 6 PB - American Institute of Physics CY - Woodbury, NY AN - OPUS4-54371 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -