First-principles study on segregation of ternary additions for MoSi2/Mo5Si3 interface

We investigate segregation behavior of additive elements M (= Ni, Cr) at the C11b/D8m interface for MoSi2- Mo5Si3 alloys, based on first-principles calculation. We first find energetically stable interface structure with interface energy of 0.08 eV/A^2. Based on the stable interface, segregation energy for additive elements is calcu- lated for individual atomic layer, which is applied to Monte Carlo statistical simulation under grand-canonical ensemble to quantitatively predict interface segregation profile. We find that our simulation successfully capture the characteristics in measured segregation tendency of (i) Similarity in strong segregation at interface both for Ni and Cr compared with bulk composition, and (ii) stronger segregation for Ni than for Cr, which can be mainly attributed to differences in calculated segregation energy. The present results indicate that measured segregated interface for MoSi2-Mo5Si3 alloys can be thermodynamically stable.