Bulk quadrupole contribution to second harmonic generation from a microscopic response function
Sprache des Titels:
Even-order nonlinear methods have proven useful tools for the analysis of centrosymmetric materials where the surface dipole contribution is often dominant. Quadrupole-order contributions from the surface discontinuity and the bulk can be on the same order of magnitude however, yet have been largely ignored in modern numerical ab initio calculations. We find that the macroscopic bulk quadrupole term inline image: inline image can be related to the first order derivatives of the microscopic response function inline image at the inline image-point and outline how a quantum-mechanical expression can be derived for a periodic system.