From the electronic structure point of view, the density of states of InPd2Cu was calculated and the Fermi level was adjusted for the homogeneity range InPd3-xCux (x = 0.1 to 1) (Fig. ). The nature of DOS remains the same throughout the homogeneity range and it seems that further substitution of Cu will increase the number of states at the Fermi level, which is thermodynamically not favourable. This suggests that the Cu-substituted compounds InPd3-xCux (x = 0.1-1) are stabilized within a very narrow VEC window; and beyond InPd2Cu, further substitution is not feasible. The substitution by Cu in the structure of binary InPd3, followed by the formation of InPd2Cu, can also be explained by chemical bonding analysis (Fig. ). It is important to note that, from In2Pd6 to In2Pd4Cu2, some In-