1306.4240 (Massimiliano Stengel)

Flexoelectricity from density functional perturbation theory    [PDF]

Massimiliano Stengel

We derive the complete flexoelectric tensor, including electronic and lattice-mediated effects, of an arbitrary insulator in terms of the microscopic linear response of the crystal to atomic displacements. The basic ingredient, which can be readily calculated from first principles in the framework of density-functional perturbation theory, is the quantum-mechanical probability current response to a long-wavelength acoustic phonon. Its second-order Taylor expansion in the wavevector q around the Gamma (q=0) point in the Brillouin zone naturally yields the flexoelectric tensor. At order one in q we recover Martin's theory of piezoelectricity [R. M. Martin, Phys. Rev. B 5, 1607 (1972)], thus providing an alternative derivation thereof. We discuss the physical interpretation of the various contributions to the flexoelectric response, either in the static or dynamic regime.

View original: http://arxiv.org/abs/1306.4240