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  2. Cation-anion radius ratio - Wikipedia

    en.wikipedia.org/wiki/Cation-anion_radius_ratio

    The radius ratio rule was first proposed by Gustav F. Hüttig in 1920. [ 5 ] [ 6 ] In 1926, Victor Goldschmidt [ 5 ] extended the use to ionic lattices. [ 7 ] [ 8 ] [ 9 ] In 1929, the rule was incorporated as the first of Pauling's rules for crystal structures .

  3. Pauling's rules - Wikipedia

    en.wikipedia.org/wiki/Pauling's_rules

    An octahedron may then form with a radius ratio greater than or equal to 0.414, but as the ratio rises above 0.732, a cubic geometry becomes more stable. This explains why Na + in NaCl with a radius ratio of 0.55 has octahedral coordination, whereas Cs + in CsCl with a radius ratio of 0.93 has cubic coordination.

  4. Fajans' rules - Wikipedia

    en.wikipedia.org/wiki/Fajans'_rules

    In inorganic chemistry, Fajans' rules, formulated by Kazimierz Fajans in 1923, [1] [2] [3] are used to predict whether a chemical bond will be covalent or ionic, and depend on the charge on the cation and the relative sizes of the cation and anion. They can be summarized in the following table:

  5. Ionic radius - Wikipedia

    en.wikipedia.org/wiki/Ionic_radius

    Ionic radius, r ion, is the radius of a monatomic ion in an ionic crystal structure. Although neither atoms nor ions have sharp boundaries, they are treated as if they were hard spheres with radii such that the sum of ionic radii of the cation and anion gives the distance between the ions in a crystal lattice .

  6. Hume-Rothery rules - Wikipedia

    en.wikipedia.org/wiki/Hume-Rothery_rules

    For interstitial solid solutions, the Hume-Rothery Rules are: Solute atoms should have a smaller radius than 59% of the radius of solvent atoms. [5] [6] The solute and solvent should have similar electronegativity. [7] Valency factor: two elements should have the same valence.

  7. Cubic crystal system - Wikipedia

    en.wikipedia.org/wiki/Cubic_crystal_system

    According to the radius ratio rule, this structure is more likely to be formed if the cation is somewhat smaller than the anion (a cation/anion radius ratio of 0.414 to 0.732). The interatomic distance (distance between cation and anion, or half the unit cell length a ) in some rock-salt-structure crystals are: 2.3 Å (2.3 × 10 −10 m) for ...

  8. Goldschmidt tolerance factor - Wikipedia

    en.wikipedia.org/wiki/Goldschmidt_Tolerance_Factor

    r B is the radius of the B cation. r O is the radius of the anion (usually oxygen). In an ideal cubic perovskite structure, the lattice parameter (i.e., length) of the unit cell (a) can be calculated using the following equation: [ 1 ]

  9. Rubidium chloride - Wikipedia

    en.wikipedia.org/wiki/Rubidium_chloride

    Because a cube has eight vertices, both ions' coordination numbers equal eight. This is RbCl's highest possible coordination number. Therefore, according to the radius ratio rule, cations in this polymorph will reach their largest apparent radius because the anion-cation distances are greatest. [4]