Shape corrections to exchange-correlation potentials by gradient-regulatedseamless connection of model potentials for inner and outer region

Shape corrections to the standard approximate Kohn-Sham exchange-correlatio n (xc) potentials are considered with the aim to improve the excitation ene rgies (especially for higher excitations) calculated with time-dependent de nsity functional perturbation theory. A scheme of gradient-regulated connec tion (GRAC) of inner to outer parts of a model potential is developed. Asym ptotic corrections based either on the potential of Fermi and Amaldi or van Leeuwen and Baerends (LB) are seamlessly connected to the (shifted) xc pot ential of Becke and Perdew (BP) with the GRAC procedure, and are employed t o calculate the vertical excitation energies of the prototype molecules N-2 , CO, CH2O, C2H4, C5NH5, C6H6, Li-2, Na-2, K-2. The results are compared wi th those of the alternative interpolation scheme of Tozer and Handy as well as with the results of the potential obtained with the statistical averagi ng of (model) orbital potentials. Various asymptotically corrected potentia ls produce high quality excitation energies, which in quite a few cases app roach the benchmark accuracy of 0.1 eV for the electronic spectra. Based on these results, the potential BP-GRAC-LB is proposed for molecular response calculations, which is a smooth potential and a genuine "local" density fu nctional with an analytical representation. (C) 2001 American Institute of Physics.