Ab initio calculation of the nonlinear susceptibility χ(2) of a crystal surface.
Résumé
The polarizability and 1st hyperpolarizability of a crystal surface were calcd. from a sum over states method using cryst. orbitals of the CRYSTAL program. The linear and nonlinear optical properties of the (001) LiF surfaces are evaluated layer by layer, showing that the response of inner layers to an elec. field tends effectively to the bulk response value while the χ(2) susceptibility components responsible of 2nd harmonic generation (SHG) are no longer equal to zero at the surface of the crystal.