CFAE Associative Substitution is the difference of crystal field stabilization energy of intermediate and reactant . And is denoted by CFAEAS. CFAE Associative Substitution is usually measured using the Diopter for Wave Number. Note that the value of CFAE Associative Substitution is always negative. Typically, the value of CFAE Associative Substitution lies in the range from 0 to 100000.