First-Principles Characterization of the P21ab Ferroelectric Phase of Aurivillius Bi2WO6

The structural, dielectric, dynamical, elastic, piezoelectric, and nonlinear optical (second-order susceptibility and Pockels tensors) properties of Bi2WO6 in its P2(1)ab ferroelectric ground state are determined using density functional theory. The calculation of infrared and Raman spectra allowed us to clarify the assignment of experimental phonon modes. The calculation of the elastic constants confirms the elastic stability of the crystal and allows us to estimate the Young and shear moduli of polycrystalline samples. The piezoelectric constants have significant intrinsic values comparable to those of prototypical ABO(3) ferroelectrics. The electro-optic response is strongly dominated by the ionic contribution of transverse optic modes, yielding a sizable Pockels coefficients around 9 pm/V along the polar direction.