Stabilities, electronic and piezoelectric properties of blue-phosphorene-phase MXs (M = Ge, Sn; X = S, Se, Te) nanotubes

By means of first-principles calculations, the stabilities, electronic and piezoelectric properties of bluephosphorene-like MXs (M = Ge, Sn; X = S, Se, Te) nanotubes (NT) were systematically investigated. Our results show that the strain energy decreases monotonically and even becomes slightly negative with increasing the tube diameter, indicative of a highly thermodynamic stability. The band gap increases gradually with increasing the tube diameter, and slowly converges to the monolayer limit. The predicted elastic constants are strongly dependent on the tube diameter and the chirality. Compared with the corresponding monolayer counterparts, the greatly increased elastic constants of NTs indicate that a reduction in dimensionality can effectively improve the rigidity. Due to the presence of centrosymmetry, the armchair-shaped NTs do not exhibit any piezoelectric behavior. In contrast, the magnitudes of piezoelectric coefficients of the zigzag-shaped NTs exhibit an interesting odd-even effect with the diameter of tube. The predicted largest piezoelectric coefficient of (27, 0) GeS NT reaches 3.20 C/m2, which is higher than most of the reported inorganic NTs. Our results suggest that these novel MXs NTs can be served as good piezoelectric materials due to high stability, suitable band gap, robust mechanical property, and adjustable piezoelectric coefficient.