The role of multisite interactions in the formation energy of bcc γ(U,Mo) disordered phase

Abstract

With the aim of emphasizing the role of bonding energy between atoms in the decomposition of the metastable gamma phase, γU(Mo), and the solubility of third elements in U–Mo alloy, we have evaluated the thermodynamic functions of the binary U–Mo system by using first-principles calculated total energies in a cluster expansion method. The minimal cluster expansion of the thermodynamic functions was determined by comparing its ability to reproduce the experimental ground state while exhibiting a good convergence of energy cluster interactions. We find that the stability of the γU(Mo) phase is dominated by a three-body multisite interaction consisting of two pairs of first neighbours and one pair of third instead of pairs' interactions as was previously proposed by other authors.