Molecular calculations of excitation energies and (hyper)polarizabilities with a statistical average of orbital model exchange-correlation potentials

An approximate Kohn-Sham exchange-correlation potential nu(xc)(SAOP) is dev eloped with the method of statistical averaging of (model) orbital potentia ls (SAOP) and is applied to the calculation of excitation energies as well as of static and frequency-dependent multipole polarizabilities and hyperpo larizabilities within time-dependent density functional theory (TDDFT). nu( xc)(SAOP) provides high quality results for all calculated response propert ies and a substantial improvement upon the local density approximation (LDA ) and the van Leeuwen-Baerends (LB) potentials for the prototype molecules CO, N-2, CH2O, and C2H4. For the first three molecules and the lower excita tions of the C2H4 the average error of the vertical excitation energies cal culated with nu(xc)(SAOP) approaches the benchmark accuracy of 0.1 eV for t he electronic spectra. (C) 2000 American Institute of Physics. [S0021-9606( 00)31102-3].