Charge transfer on the metallic atom-pair bond, and the crystal structures adopted by intermetallic compounds

Rajasekharan, T.; Seshubai, V.

doi:10.1107/S0108767311044151

Figure 9
Plot of the change in radius of the minority atom on alloying R_A - r_A versus R_A/R_B for 240 AuCu₃-type compounds. r_A is the radius of the A atom in the structure and is calculated from the lattice parameter as a/[2(2^1/2)]. The points can be fitted to the equation R_A - r_A = 2.313 + 3.255(R_A/R_B) - 0.929(R_A/R_B)². R_A - r_A is almost zero when R_A/R_B = 1. The compounds with $[{\varphi}_{A}]$ > $[{\varphi}_{B}]$ (red squares) have R_A - r_A negative, and those with $[{\varphi}_{A}]$ < $[{\varphi}_{B}]$ (black circles) have R_A - r_A positive. The change in size of the atoms is in accordance with the hypothesis that the more electronegative atoms transfer electrons to the less electronegative ones on alloying.