Surface parameters of ferritic iron-rich Fe-Cr alloy

TL;DR

This study uses first-principles calculations to analyze how chromium concentration affects the surface energy and stress of Fe-Cr alloys, revealing magnetic origins and segregation effects on surface stability.

Contribution

It provides new insights into the surface parameters of Fe-Cr alloys, including the impact of Cr addition and segregation on surface stability and magnetic properties.

Findings

Cr increases surface energy of Fe-Cr alloys

Cr addition decreases surface stress of the alloy

Higher Cr concentration stabilizes the (100) surface against reconstruction

Abstract

Using first-principles density functional theory in the implementation of the exact muffin-tin orbitals method and the coherent potential approximation, we studied the surface energy and the surface stress of the thermodynamically most stable surface facet (100) of the homogeneous disordered body-centred cubic iron-chromium system in the concentration interval up to 20 at.% Cr. For the low-index surface facets of Fe and Cr, the surface energy of Cr is slightly larger than the one of Fe, while the surface stress of Cr is considerably smaller than the one of Fe. We find that Cr addition to Fe generally increases the surface energy of the Fe-Cr alloy, however, an increase of the bulk amount of Cr also increases the surface stress. As a result of this unexpected trend, the (100) surface of Fe-Cr becomes more stable against reconstruction with increasing Cr concentration. We show that the observed trends are of magnetic origin. In addition to the homogeneous alloy case, we also investigated the impact of surface segregation on both surface parameters.