Ionic order cap is usually enriched with egg-and-dart. Since Vitruvius, a female character has been ascribed to the Ionic (in contrast to the masculine Doric). The major features of the Ionic order are the volutes of its capital, which have been the subject of much theoretical and practical discourse, based on a brief and obscure passage in Vitruvius. The only tools required to design these features were a straight-edge, a right angle, string (to establish half-lengths) and a compass. Below the volutes, the Ionic column may have a wide collar or banding separating the capital from the fluted shaft (as in, for
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