A new type of two-dimensional piezoelectric material: MOene based on Ti2O and its Janus structure.

[Display omitted] • The novel 2H-MOene and its Janus structure are predicted to be a promising piezoelectric material. • The novel 2D-MOene shown a superior piezoelectric coefficient d11 (d11 = 6.09 pm/V for Ti2OH2). • MOene and its Janus structure satisfy the rule of d 11 (_F) < d 11 (_Cl) < d 11 (_Br) < d 11 (_I). Two-dimensional (2D) piezoelectric materials have been widely studied because of their broad application prospects. In this paper, the piezoelectric properties of a MXene-like 2D material (MOene) and its Janus structure are reported by first-principles calculations. The dynamic stability of these 2D materials are verified based on phonon spectra. The semiconductor properties of materials are based on the calculation of energy bands. The origin of piezoelectric polarization of MOene and its Janus structure is explained based on differential charge density and Bader charge analysis. The piezoelectric stress tensor of the material is calculated based on density functional perturbation theory (DFPT). The theoretical prediction results show that the piezoelectric properties of MOene and its Janus structure are better than those of 2D 2H-MoS 2 , and the in-plane piezoelectric coefficient d 11 of Ti 2 OH 2 reaches 6.09 pm/V. Our research shows that MOene and its Janus structure add an important member to the 2D piezoelectric material library, and provide a new sample for the study of piezoelectric properties based on the 2D material library. [ABSTRACT FROM AUTHOR]