FREQUENCY-DEPENDENT 2ND HYPERPOLARIZABILITIES USING COUPLED-CLUSTER CUBIC RESPONSE THEORY

The coupled cluster cubic response function is derived using a time-av eraged quasienergy Lagrangian and Fourier component variational pertur bation theory. The obtained expressions are in accord with the 2n + 1 and 2n + 2 rules. The first implementation of the cubic response funct ion is reported for frequency-dependent second hyperpolarizabilities f or a coupled cluster singles and doubles wavefunction and sample calcu lations are presented for hyperpolarizabilities of N-2, for several th ird-order optical processes. The results are in excellent agreement wi th recent experiments for electric field induced second harmonic gener ation. (C) 1998 Elsevier Science B.V.