Correlation of octahedral ion electronegativity with band frequency appears to best account for observed OH stretch frequencies in the di- and trioctahedral minerals potassic mica, talc and saponite. The site of charge substitution in the octahedral layer or in the tetrahedral layer affects the band frequencies also. Band displacements are the same in micas when charge increases in the tetrahedral layer. Substitution of ions of the same charge in the tetrahedral site does not change vibration frequencies as a function of the electronegativity of the ion substituted, but there is a correlation between unit cell size and frequency shift. This is attributed to hydrogen-oxygen repulsion between ions in octahedral and tetrahedral layers. Electronic configuration of the ions bonded and involved in the bonding of the oxygen of the OH units seems to be the major factor in determining the OH stretch band frequency.--Modified journal abstract.

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