FIRST-PRINCIPLES CALCULATION OF BULK SUSCEPTIBILITY FOR 2ND-HARMONIC GENERATION IN CRYSTALLINE C-60

The hyperpolarizabilities for electric dipole second-harmonic generati on (SHG) due to the bilinear combination of an electric field and eith er the electric-field gradient (mu(eeq)) Or the associated magnetic fi eld (tau(eem)), and for electric quadrupole SHG quadratic in the elect ric field (mu(qee)) have been calculated for the C-60 molecule at pump photon energies from 0.5 to 2.2 eV using the valence effective Hamilt onian method with a minimal STO-3G basis; magnetic dipole SHG quadrati c in the electric field (tau(mee)) is zero by symmetry in C-60 The coe fficients exhibit resonances at photon energies near 1.9 for mu(eeq), 1.4 for mu(qee), and 2.0 eV for tau(eem). They are combined with empir ical local-field factors and a theoretical local field-gradient tenser to calculate the composite susceptibility chi((2)) for SHG from cryst alline C-60 in the same energy range. The susceptibility shows several resonances that arise from those in mu(eeq), mu(qee) and tau(eem). Th e results are able to reproduce the magnitudes and signs reported expe rimentally, subject to a sensitive dependence on photon energy near re sonances. (C) 1998 American Institute of Physics.