Dynamic Simulation of Structural Phase Transitions in Magnetic Iron

Abstract

The occurrence of bcc-fcc ($\alpha$-$\gamma$) and fcc-bcc ($\gamma$-$\delta$) phase transitions in magnetic iron stems from the interplay between magnetic excitations and lattice vibrations. However, this fact has never been proven by a direct dynamic simulation, treating non-collinear magnetic fluctuations and dynamics of atoms, and their coupling at a finite temperature. Starting from a large set of data generated by ab initio simulations, we derive non-collinear magnetic many-body potentials for bcc and fcc iron describing fluctuations in the vicinity of near perfect lattice positions. We then use spin-lattice dynamics simulations to evaluate the difference between free energies of bcc and fcc phases, assessing their relative stability within a unified dynamic picture. We find two intersections between the bcc and fcc free energy curves, which correspond to $\alpha$-$\gamma$ bcc-fcc and $\gamma$-$\delta$ fcc-bcc phase transitions. The maximum fcc-bcc free energy difference over the temperature interval between the two phase transition points is 2 meV, in agreement with other experimental and theoretical estimates.

References in corpus (6)

• Nonequilibrium free-energy calculation of solids using LAMMPS
• Potfit: effective potentials from ab-initio data
• Effective potentials for quasicrystals from ab-initio data
• Magnetism of iron: from the bulk to the monoatomic wire
• Electronic correlations determine the phase stability of iron up to the melting temperature
• Reinventing atomistic magnetic simulations with spin-orbit coupling

Cited by in corpus (4)

• The Dynamics of Magnetism in Fe-Cr Alloys with Cr Clustering
• Magnetochemical coupling effects on thermodynamics, point-defect formation and diffusion in Fe-Ni alloys: a theoretical study
• Simulation of thermodynamic properties of magnetic transition metals from an efficient tight-binding model
• The microscopic Einstein-de Haas effect