Factors influencing solid-state structure—an analysis using pseudopotential radii structural maps

Structural sorting maps using R_σR_π, r₊r_-, r_σAr_σB, and χAχB are compared for AB, AB₂ octets and double octets, and AB₂X₄ spinels. With the use of r₊r_-, the crystal ionic radii, the sorting is tolerable only if the usual restrictions of the mechanical model (radius ratio rules) are relaxed. R_σR_π are poor indices for AB₂ and AB₂X₄, but r_σAr_σB and χAχB are excellent for all three systems. It is suggested that the traditional packing ideas based on size (and viewed semiquantitatively here using the r_σ^ξ) are directly related to modern charge-control aspects (via electronegativity differences) of molecular structures, and both can be viewed as very important factors in determining structural preference.