Study of elastic and piezoelectric properties of two-dimensional hexagonal III-V binary compounds: First-principles calculations

In this work, using plane wave method in the framework of density-functional theory, we calculated clamped-ion and relaxed-ion elasticity, stress and strain piezoelectric independent coefficients for seven stable combinations of honeycomb monolayers XY (X:B,Al,Ga,In ; Y:N,P,As,Sb). The coefficients calculations by two methods of density functional perturbation theory (DFPT) and finite difference (FD) have been done with very good agreement. The results showed that seven combined BN, BP, BAs, BSb, AlN, GaN and InN have honeycomb structure and polarized, and because of the 3m point-group symmetry in this class of 2D materials only exhibit two  independent  elasticity coefficients and one independent stress or strain piezoelectric coefficient. Among the seven combinations, the highest relaxed-ion piezoelectric coefficients calculated for AlN(d11=3.05 pm/V) and InN (d11=7.01 pm/V) .The group of 2D polarized materials that exhibit simultaneously piezoelectric and semiconducting properties are good candidates for use in the new branch of nanotechnology called nanopiezotronics.