Ionic order edifices antiques de Rome" (Paris 1682). Ionic order The Ionic order forms one of the three classical orders of classical architecture, the other two canonic orders being the Doric and the Corinthian. There are two lesser orders: the Tuscan (a plainer Doric), and the rich variant of Corinthian called the composite order, both added by 16th-century Italian architectural writers, based on Roman practice. Of the three canonic orders, the Ionic order has the narrowest columns. The Ionic capital is characterized by the use of volutes. The Ionic columns normally stand on a base which separates the shaft of the column
Ionic radius radii. The relation between soft-sphere ionic radii, formula_2 and formula_3, and formula_1, is given by formula_5, where formula_6 is an exponent that varies with the type of crystal structure. In the hard-sphere model, formula_6 would be 1, giving formula_8. In the soft-sphere model, formula_6 has a value between 1 and 2. For example, for crystals of group 1 halides with the sodium chloride structure, a value of 1.6667 gives good agreement with experiment. Some soft-sphere ionic radii are in the table. These radii are larger than the crystal radii given above (Li, 90 pm; Cl, 167 pm). Inter-ionic separations calculated