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Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides
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1976
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EngineeringComputational ChemistryChemistryInorganic MaterialInorganic CompoundInteratomic DistancesLocalized ElectronsMaterials ScienceInorganic ChemistryPhysicsChemical BondQuantum ChemistryCrystallographyPolyhedral DistortionSystematic StudiesNatural SciencesApplied PhysicsEffective Ionic RadiiIon Structure
The paper revises Shannon & Prewitt effective ionic radii, noting that factors such as polyhedral distortion, partial occupancy, covalence, metallic character, and delocalized electrons influence radii additivity and bond lengths. The study aims to revise effective ionic radii to encompass unusual oxidation states and coordinations. Revisions are derived from new structural data, empirical bond strength–bond length relationships, and plots of radii versus volume, coordination number, and oxidation state. The revised radii reveal that octahedral distances for Nb5+–O and Mo6+–O depend linearly on distortion, cation occupancy reduction lengthens Li+, Na+, and Ag+–O bonds, covalence shortens many transition‑metal–X and M–H bonds with decreasing electronegativity, while Zn2+, Cd2+, In2+, Pb2+, and Ti2+ show smaller effects, and bonds with delocalized electrons are markedly shorter.
The effective ionic radii of Shannon & Prewitt [Acta Cryst. (1969), B25, 925-945] are revised to include more unusual oxidation states and coordinations. Revisions are based on new structural data, empirical bond strength-bond length relationships, and plots of (1) radii vs volume, (2) radii vs coordination number, and (3) radii vs oxidation state. Factors which affect radii additivity are polyhedral distortion, partial occupancy of cation sites, covalence, and metallic character. Mean Nb5+-O and Mo6+-O octahedral distances are linearly dependent on distortion. A decrease in cation occupancy increases mean Li+-O, Na+-O, and Ag+-O distances in a predictable manner. Covalence strongly shortens Fe2+-X, Co2+-X, Ni2+-X, Mn2+-X, Cu+-X, Ag+-X, and M-H- bonds as the electronegativity of X or M decreases. Smaller effects are seen for Zn2+-X, Cd2+-X, In2+-X, pb2+-X, and TI+-X. Bonds with delocalized electrons and therefore metallic character, e.g. Sm-S, V-S, and Re-O, are significantly shorter than similar bonds with localized electrons.