Calculation of core-level-shifts from an alternative ionicity scale

Shevchik et al.^1,2 proposed an electrostatic model relating charge transfer between ions and chemical shifts in ionic compounds. The charge transfer can be calculated from the ionicity. If one uses Phillips ionicities one obtains the wrong sign for the calculated core-level-shifts of copper halides as it is pointed out by Shevchik et al.^1,2. We show that the shifts can be computed fairly successfully if one uses an alternative definition of ionicity recently proposed⁴. Using this definition it is further shown that the charge transfer is identical with the longitudinal (Callen) charge of a crystal.