  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.
