Table 2.
Piezoelectric tensor elements and spontaneous polarizations of NbOX2.
| Formula | e11 | e12 | e13 | e26 | e35 | d11 | d12 | d26 | Px |
|---|---|---|---|---|---|---|---|---|---|
| NbOCl2 | 25.1 | −1.1 | −0.4 | 0.8 | 0.0 | 27.4 | −4.1 | 5.4 | 185 |
| NbOBr2 | 26.4 | −1.0 | −0.4 | 0.8 | 0.0 | 30.0 | −4.1 | 5.8 | 170 |
| NbOI2 | 31.6 | −1.0 | −0.3 | 0.7 | 0.0 | 42.2 | −5.1 | 5.2 | 143 |
Sheet piezoelectric stress tensor elements eij are in units of 10−10 C m−1 and piezoelectric strain tensor elements dij are in pm V−1. Piezoelectric tensor elements that are zero due to symmetry of the space group are omitted here. Spontaneous polarization along the x-direction (Px) in pC m−1 is calculated as the difference between the polarization of the equilibrium and symmetric structures.