Our calculated e ij tensors are given in the Supplementary Information. Table shows computed e elc 33 , e ion 33 , and e 33 . We notice that both value and sign of the calculated e elc 33 , e ion 33 , and e 33 by LCALCEPS and DFPT are quite consistent with these obtained by the slope method (Figure ). The magnitude of e 33 increases as doping concen-tration increases. Overall, our e 33 values are quite comparable with that of other known negative piezoelectricsfor example, e 33 of Ga 0.125 B 0.875 N (-1.164 C/m 2 ) is comparable to that of NaZnSb (-1.23 C/m 2 ) .