C and N effect on magnetic coupling and vibrational properties of bcc and fcc-FeMnCr alloys: DFT study

Abstract

In this work we report, magnetic and thermal properties of the bcc-Fe0.52MnxCr0.28-xCu0.06Mo0.10C0.012N0.014 (xMn = 5.77, 11.51 and 17.22 wt%) and the fcc-Fe0.63MnxCr0.26-xCu0.03Mo0.05C0.006N0.007 (xMn = 8.98, 11.95 and 14.92 wt%) alloys, applying the pseudo-potential Density Functional Theory (PP-DFT). The obtained results show that magnetic properties of these alloys are governed by Mn concentrations and C, N additions. The magnetic moments at each atom depend strongly on Mn concentrations as well as on the presence of C, N atoms. The C, N or both CN additions into octahedral sites do not affect the magnetic coupling between atoms. The quasi-harmonic Debye model is successfully applied to predict thermal properties of these alloys. The bulk modulus, volume expansion and Gibbs free energy are significantly affected by temperature, Mn concentrations and C, N additions in both bcc and fcc alloys. Whereas, vibrational entropy is more affected by bcc–fcc phase transition than C, N addition and Mn concentration.