The paper by Fabio Bernardini, Vincenzo Fiorentini, and David Vanderbilt investigates the spontaneous polarization, dynamical Born charges, and piezoelectric constants of III-V nitrides (AlN, GaN, and InN) using the Berry phase approach to polarization in solids. The study reveals that these nitrides exhibit significantly larger piezoelectric constants (up to 10 times those of conventional III-V and II-VI compounds) and comparable values to ZnO. Notably, the sign of the piezoelectric constants is positive, similar to II-VI compounds, and the spontaneous polarization is very large, particularly in AlN, which is the largest reported value for any binary compound among tetrahedrally bonded semiconductors. The results suggest that III-V nitrides share some properties with II-VI oxides and ferroelectric perovskites, despite being conventional III-V materials. The study also highlights the importance of these properties for the design of nitride-based piezoelements and multilayer structures.The paper by Fabio Bernardini, Vincenzo Fiorentini, and David Vanderbilt investigates the spontaneous polarization, dynamical Born charges, and piezoelectric constants of III-V nitrides (AlN, GaN, and InN) using the Berry phase approach to polarization in solids. The study reveals that these nitrides exhibit significantly larger piezoelectric constants (up to 10 times those of conventional III-V and II-VI compounds) and comparable values to ZnO. Notably, the sign of the piezoelectric constants is positive, similar to II-VI compounds, and the spontaneous polarization is very large, particularly in AlN, which is the largest reported value for any binary compound among tetrahedrally bonded semiconductors. The results suggest that III-V nitrides share some properties with II-VI oxides and ferroelectric perovskites, despite being conventional III-V materials. The study also highlights the importance of these properties for the design of nitride-based piezoelements and multilayer structures.