Figure 4.

Same as Fig. 3 but in non-logarithmic scale for comparison of two kinds of local perturbations, i.e. geometric (displacement by 0.1 Å, repeated from Fig. 3) and chemical (vacancy or impurity substitution). The impurity has the same number of valence electrons as the original atom when substituting Si by Ge, Cl by Br, Na by K, Cu by Ag while the number of valence electrons differ by one when substituting Si by P, Cl by S, Na by Mg, Cu by Zn.