The width and energy of low-index interfacial boundaries (IFBs) in Ni–Ni3Al are calculated using first-principles methods for temperatures ranging from 0 to 1300 K. The low-temperature, coherent and chemically sharp (100), (110) and (111) IFBs are studied using conventional spin-polarized density functional methods. Cluster expansion methods, as implemented in the ATAT software suite, are used ...