DYNAMIC POLARIZABILITIES AND EXCITATION-SPECTRA FROM A MOLECULAR IMPLEMENTATION OF TIME-DEPENDENT DENSITY-FUNCTIONAL RESPONSE THEORY - N-2 AS A CASE-STUDY

We report the implementation of time-dependent density-functional resp onse theory (TD-DFRT) for molecules using the time-dependent local den sity approximation (TDLDA). This adds exchange and correlation respons e terms to our previous work which used the density-functional theory (DFT) random phase approximation (RPA) [M. E. Casida, C. Jamorski, F. Bohr, J. Guan, and D. R. Salahub, in Theoretical and Computational Mod eling of NLO and Electronic Materials, edited by S. P. Kama and A. T. Yeates (ACS, Washington, D.C., in press)], and provides the first prac tical, molecular DFT code capable of treating frequency-dependent resp onse properties and electronic excitation spectra based on a formally rigorous approach. The essentials of the method are described, and res ults for the dynamic mean dipole polarizability and the first eight ex citation energies of N-2 are found to be in good agreement with experi ment and with results from other ab initio methods. (C) 1996 American Institute of Physics.