Mean-field approach for Anderson-type off-diagonal disorder

We report a generalized auxiliary coherent medium theory to settle the longstanding challenge of Anderson-type off-diagonal disorder (AODD) for simulating disordered alloys. The AODD is transformed into a diagonal-like disorder with a weighted discrete distribution in an auxiliary medium. This approach is demonstrated for simulating the phonon spectral in NiFe and NiPt alloys, and it is found that accounting for AODD substantially enhances the phonon linewidth to agree well with the supercell and experimental results, compared to results with averaged-value ODD. This paper provides an effective approach to treat the large fluctuation in ODD in disordered materials, presenting an important progress for mean-field simulations in the embedding framework.