“…Among the 18 compounds covered in this study, we identify 11 compounds (LiGeN, NaGeN, KGeN, KGeP, LiSnN, NaSnN, NaSnP, NaSnAs, KSnN, KSnP, and KSnAs) with the NLPE. Moreover, we note that the calculated | d 33 | values of 4 compounds (10.05 pC N −1 for NaGeSb, 8.68 pC N −1 for KGeSb, −9.61 pC N −1 for LiSnN, and 7.41 pC N −1 for KSnSb) are comparable in magnitude to that of AlN (a typical piezoelectric material that is widely used as energy harvesters 59 and sensors 60 due to its high d 33 of 5.5 pC N −1 61 ), and hence these materials may have potential applications in electromechanical devices such as piezoelectric actuators 62 due to their relatively large piezoelectric response. It is worth mentioning that the d 33 is related to the e ij via the elastic compliance tensor C ij (
), and hence the difference in the | d 33 | may be substantial especially for compounds with a large | d 33 | such as NaGeSb and KGeSb ( d 33 = 10.05 pC N −1 for NaGeSb; d 33 = 8.68 pC N −1 for KGeSb,) even though they are chemically similar (for NaGeSb, Δ χ = 0.71; for KGeSb, Δ χ = 0.73), as shown in Fig.…”