Non-linear electro-elastic coupling in non-centrosymmetric materials

We propose an extended symmetry-based thermodynamical model of third-order electro-elastic coupling. The entanglement of electrostriction non-linear piezoelectricity and other non-linear phenomena, is studied in details at the same level of theory. Symmetry properties of materials and nanostructures are taken into account. Density Functional Theory (DFT) is used to calculate the complete set of linear and non-linear coefficients. Electrostriction dominates for nitride compounds in the Würtzite structure, but non-linear elasticity and piezoelectricity must be taken into account for strain and electric field evaluation.