FIG. 1: Cantilever beam(initial configuration). where W is an energy density of deformation and polarization, a$_{ij}$ , b$_{ijkl}$ , c$_{ijkl}$ , d$_{ijk}$ , e$_{ijkl}$ , f$_{ijkl}$ , g$_{ijk}$ are the components of reciprocal dielectric susceptibility, polarization gradient- polarization gradient coupling tensor, elastic tensor, piezoelectric tensor, polarization gradient-strain coupling tensor, flexoelectric tensor, and polarization-polarization gradient coupling tensor, respectively, ϕ is the potential of electric field. Since the components of the stress tensor and the electric field vector E$_{i}$ = − ϕ ′ i are expressed as we have Compare (1), (2), and the second equation of (5), we conclude that flexoelectric tensor f$_{ijkl}$ T$_{ij}$ = ∂W ∂S$_{ij}$ , E$_{i}$ = − ∂W ∂P$_{i}$ , T$_{ij}$ = c$_{ijkl}$S$_{kl}$ + d$_{ijk}$P$_{k}$ + e$_{ijkl}$P$_{k,l}$ − E$_{i}$ = a$_{ij}$P$_{j}$ + d$_{ijk}$S$_{jk}$ + f$_{ijkl}$u$_{i,jk}$ (5) 4