On Feb 18, 2008, at 14:08 , xu yuehua wrote: > i am writing to enquire that is there a way to get the second order > coefficient of Nonlinear Optical within PWSCF, directly or indirectly.
second-order nonlinear optical coefficients, i.e. \gamma in the following formula, where P is the induced polarization and E the electric field: P=\alpha E + \beta E^2 + \gamma E^3 ? this is the fourth-order derivative of the energy wrt electric field and can be calculated using the second-order response to an applied electric field. The latter is calculated by the phonon code for the Raman calculation. The code already calculates the nonlinear optical coefficient \beta (called "electro-optical coefficients": I do not think this is correct, by the way). Static calculations, though (\omega=0), and no ultrasoft PP. So all ingredients are there, but require some programming. It is something that I wanted to do (and still want to do: it is useful to estimate how nonlinear optical properties change in phtalocyanines when deposited on some surfaces and doped), but it requires an amount of patience that I am afraid I no longer have. Anybody interested? Paolo --- Paolo Giannozzi, Dept of Physics, University of Udine via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
