The electronic structure of these three polymorphs is complemented with crystal orbital Hamilton population (COHP) analysis to extract the detailed bonding information. COHP is a theoretical bond-detecting tool for solids that partitions the band-structure energy into orbital-pair interactions. It is "bond-weighted" density-of-states between a pair of adjacent atoms. A COHP diagram indicates bonding and antibonding contributions to the band-structure energy, a positive -COHP means the population of bonding states and a negative -COHP means the population of anti-bonding states. It is evident and expected from the structures that the hetero-atomic In-Pd contacts are major in number and contribute maximum towards the overall stability. Interestingly, the ZrAl3-type compound possesses a nearly optimized In-Pd bonding scenario, i.e. least occupied antibonding states, and the crossover between bonding and anti-bonding states falls very near to the Fermi level. The abundance of the anti-bonding population for the In-Pd bonds follows the order ZrAl3-type < TiAl3-type < AuCu type (Fig. ). In-fact, the negative integrated COHP (-ICOHP) of the most frequent and majorly contributing In-Pd bonds are in the order of ZrAl3-type > TiAl3-type > AuCu type. This order of negative ICOHP provides a clear indication of the strength of individual contacts (Table ). Longer annealing time at higher temperature leads to more optimized heteroatomic bonding scenario (ZrAl3-type); shorter reaction time doesn't allow the system to build the extended ordering between the heteroatoms, driving towards a disordered structuretype (AuCu-type). TiAl3-type falls between these two types. The partial covalent character of these heteroatomic contacts is also reflected in the average Mulliken and Löwdin charges on individual elements calculated from LOBSTER (Table ). Thus, the extent of crystallographic ordering, electronic stability, and chemical bonding is controlled mostly by reaction conditions as the system under investigation possesses the same valence electron concentration (VEC). This also sets a nice proof and theoretical justification for the 'Ostwald's step rule' .