Compositional disorder and its influence on the structural, electronic and magnetic properties of MgC(Ni_{1-x}Co_{x})_{3} alloys using first-principles

TL;DR

This study uses first-principles calculations to explore how compositional disorder affects the structural, electronic, and magnetic properties of MgC(Ni_{1-x}Co_{x})_{3} alloys across different concentrations, revealing key variations and magnetic behaviors.

Contribution

It introduces a comprehensive first-principles approach to analyze disorder effects on alloy properties, including magnetic state corrections and volume dependence, over the entire composition range.

Findings

Lattice parameter and bulk modulus vary independently at x~0.75.

Magnetic ground state overestimations are corrected for 0.0≤x≤0.3.

Multiple magnetic states may exist at x~0.75, needing further study.

Abstract

First-principles, density-functional based electronic structure calculations are carried out for MgC(Ni_{1-x}Co_{x})_{3} alloys over the concentration range 0\leq x\leq1, using Korringa-Kohn-Rostoker coherent-potential approximation (KKR CPA) method in the atomic sphere approximation (ASA). The self-consistent calculations are used to study the changes as a function of x in the equation of state parameters, total and partial densities of states, magnetic moment and the on-site exchange interaction parameter. To study the magnetic properties as well as its volume dependence, fixed-spin moment calculations in conjunction with the phenomenological Landau theory are employed. The salient features that emerge from these calculations are (i) a concentration independent variation in the lattice parameter and bulk modulus at x~0.75 with an anomaly in the variation of the pressure derivative of bulk modulus, (ii) the fixed-spin moment based corrections to the overestimated magnetic ground state for 0.0\leq x\leq0.3 alloys, making the results consistent with the experiments, and (iii) the possibility of multiple magnetic states at x~0.75, which, however, requires further improvements in the calculations.