A comparison of excited state properties for iterative approximate tripleslinear response coupled cluster methods

A computational study of the potential energy curves of the (1)Pi state of BH, (1)Pi state of CH+, (1)Sigma (u) and (1)Pi (u) states of C-2, (1)Pi sta te of CO, and (1)Pi (g) and (1)Sigma (-)(u) states of N-2 is carried out wi th the CC3 and CCSDT-3 corrections to EOMEE-CCSD. Good agreement in structu re, vibrational frequencies, and excitation energies of these iterative tri ples-corrected methods with respect to experiment is found for most of thes e examples. However, deficiencies in the approximate treatment of triples i s evident for BH and CH+. (C) 2001 Elsevier Science B.V. AE rights reserved .