ERIC Number: EJ1159465
Record Type: Journal
Publication Date: 2017-Oct
Abstractor: As Provided
Radius Ratio Rule Rescue
Michmerhuizen, Anna; Rose, Karine; Annankra, Wentiirim; Vander Griend, Douglas A.
Journal of Chemical Education, v94 n10 p1480-1485 Oct 2017
Making optimal pedagogical and predictive use of the radius ratio rule to distinguish between solid state structures that feature tetrahedral, octahedral and cubic holes requires several updated insights. A comparative analysis of the Born-Landé equation for lattice energy is developed to show that the rock salt structure is a suitable choice for radius ratios between 0.326 and 1.00. The lower bound is the ratio at which the energy of the rock salt structure matches that of the zinc blende structure, all other things being equal. The upper bound extends all the way to unity because the relative energy of the rock salt and CsCl structures are within 1% of each other for radius ratios above 0.717, which is the ratio at which the energy of the rock salt structure matches that of the CsCl structure. Geometric analysis of 154 1:1 ionic compounds that can potentially adopt the zinc blende, rock salt, or CsCl structure demonstrates that while existing ionic radii can be used for predictions with substantial success, a more applicable set of predictive ionic radii based on cubic lattice parameters can be deduced.
Descriptors: Mathematical Concepts, Chemistry, Comparative Analysis, Geometric Concepts, Energy, Stoichiometry
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Publication Type: Journal Articles; Reports - Research
Education Level: N/A
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