EFFECT OF MEDIUM POLARITY ON THE 2ND-ORDER POLARIZABILITY OF AN OCTUPOLAR CHROMOPHORE - AN AB-INITIO REACTION FIELD-STUDY OF TRIAMINOTRINITROBENZENE

The Self-Consistent Reaction Field theory (extended to include an elli psoidal cavity for the solute and a multipolar expansion of the field) is used to investigate the influence of medium polarity on the second -order nonlinear optical response of the prototypical octupolar compou nd 1,3,5-triamino-2,4,6-trinitrobenzene, TATE. Despite the absence of any dipole moment in TATE, the effect of medium polarity is found to b e significant; for instance, the beta(zzz) tensor component of TATE is calculated to be twice as large in dichloromethane (electric permitti vity epsilon = 9.1) as in the gas phase (epsilon = 1). This enhancemen t factor is similar to, though somewhat smaller than the one calculate d for the dipolar counterpart of TATE, i.e. p-nitroaniline.