Dr. Eduardo Mendive-Tapia, University of Barcelona
Host: Manuel Dos Santos Dias, Theoretical and Computational Physics, SCD
Friday 16th September 2022 @ 11:00-12:00
Ab initio calculation of the magnetic Gibbs free energy using magnetically constrained supercells: electronic and magnetoelastic mechanisms of first-order transitions
First-order (discontinuous) phase transitions between magnetic states can provide huge entropy and temperature changes driven by the application of small external stimuli, the so-called caloric effect exploited in the design of cooling cycles [1]. We present an approach based on density functional theory (DFT) calculations of magnetically constrained supercells to compute the magnetic Gibbs free energy of materials [2,3]. The minimization of this free energy predicts and explains the character of phase transitions at finite temperature in terms of both purely electronic and magnetoelastic mechanisms, the former arising from the presence of multisite magnetic interactions [4]. The performance of two different DFT codes, the Vienna Ab Initio Simulation package (VASP) and the linear-scaling KKR-nano suitable for thousands of atoms (https://jukkr.fz-juelich.de), will be demonstrated. Results obtained for some materials, including the triangular antiferromagnetic state in antiperovskite systems, will be shown and compared with experiment.
[1] X. Moya et al., Nature Materials 13, 439 (2014).
[2] B.L. Gyorffy et al., J. Phys. F: 15, 1337 (1985).
[3] E. Mendive-Tapia, J. Neugebauer, and T. Hickel, Phys. Rev. B 105, 064425 (2022).
[4] E. Mendive-Tapia and J.B. Staunton, Phys. Rev. B 99, 144424 (2019).
