The substitution of ReO 4 for IO 4 for both the HQ and dabco compounds resulted in a decrease in the piezoelec-tric response, see Sec. II B. Still, in both cases, the shear piezoelectric responses are among the highest predicted responses in this work. Rhenium is a high-cost element, and this work shows that substituting ReO 4 for IO 4 can be used to reduce the price of a molecular piezoelectric if a reduction of the piezoelectric coefficients is acceptable.