Plot of the change in radius of the minority atom on alloying RA − rA versus RA/RB for 240 AuCu3-type compounds. rA is the radius of the A atom in the structure and is calculated from the lattice parameter as a/[2(21/2)]. The points can be fitted to the equation RA − rA = 2.313 + 3.255(RA/RB) − 0.929(RA/RB)2. RA − rA is almost zero when RA/RB = 1. The compounds with > (red squares) have RA − rA negative, and those with < (black circles) have RA − rA 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.