The effect of spin-polarization, atomic ordering and charge transfer on the stability of CoCrNi medium entropy alloy

článek v časopise ve Web of Science, Jimp

en

The aim of this paper is to determine the effects of spin-polarization and atomic ordering on the phase stability of the medium entropy alloy CoCrNi by employing density functional theory calculations. We have found that high Cr ordering causes stabilisation of both the fcc and hcp structures compared to fully disordered alloy, while high Ni ordering leads to destabilisation of the hcp structure but has no effect on the fcc structure. The differences in the mutual stability of fcc and hcp structures for alloys with different levels of ordering are accompanied by differences in the distribution of local magnetic moments. However, their analysis revealed a generally increasing trend in the magnitude of the magnetic moment with the increasing number of Cr atoms in the 1st nearest neighbours (NN) shell for all Co, Cr, and Ni elements. Moreover, the charge analysis revealed a charge transfer from Cr to the other two elements in the alloy and also its dependence on the number of Cr atoms in the 1st NN shell. Thus, we have described the clear indirect dependence of the magnetic moment of all elements in this alloy on the ongoing charge transfer. This also points to the possibility that the charge transfer has the more important effect on stabilisation of particular atomic ordering rather than the spin-polarization as the same behaviour of charge transfer was observed also for results obtained without spin-polarization.

The aim of this paper is to determine the effects of spin-polarization and atomic ordering on the phase stability of the medium entropy alloy CoCrNi by employing density functional theory calculations. We have found that high Cr ordering causes stabilisation of both the fcc and hcp structures compared to fully disordered alloy, while high Ni ordering leads to destabilisation of the hcp structure but has no effect on the fcc structure. The differences in the mutual stability of fcc and hcp structures for alloys with different levels of ordering are accompanied by differences in the distribution of local magnetic moments. However, their analysis revealed a generally increasing trend in the magnitude of the magnetic moment with the increasing number of Cr atoms in the 1st nearest neighbours (NN) shell for all Co, Cr, and Ni elements. Moreover, the charge analysis revealed a charge transfer from Cr to the other two elements in the alloy and also its dependence on the number of Cr atoms in the 1st NN shell. Thus, we have described the clear indirect dependence of the magnetic moment of all elements in this alloy on the ongoing charge transfer. This also points to the possibility that the charge transfer has the more important effect on stabilisation of particular atomic ordering rather than the spin-polarization as the same behaviour of charge transfer was observed also for results obtained without spin-polarization.

Ab initio calculations; Medium entropy alloy; Short-range ordering; Magnetism; Charge transfer; Phase stability

17.04.2023

ELSEVIER SCIENCE SA

LAUSANNE

0254-0584

304

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127783–-

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