Renner–Teller effect in five-atomic molecules: Ab initio investigation of the spectrum of

Renner–Teller effect in six-atomic molecules: Ab initio investigation of the vibronic spectrum of

“…However, we did not achieve any significant improvement of our results produced by using the aug-cc-pVTZ basis. [26]) that the discrepancies between the present and Szczepansky's results have to be ascribed to the small basis set and particularly the absence of the diffuse basis functions that are necessary for reliable description of anions, employed in the former work.…”

“…(67), namely All the formulae (61)-(69), as well as those given in Appendix A, reduce to the corresponding formulae for five-, four-, and three-atomic molecules, if we put n = 3 (i.e. S = 5), n = 2 (S = 4), and n = 1 (S = 3), respectively [21,26].…”

“…In two recent studies, [22,23], it was shown that the RT effect in tetra-atomic molecules can be considered as a superposition of three most important mechanisms that violate the BO approximation, namely the vibronic coupling caused by distortion of linearity, conical intersections (like in the case of the Jahn-Teller effect [24]), and avoided crossings of potential surfaces. Finally, the model for handling the RT effect was generalized to linear molecules with arbitrary number of atoms [25] and applied to the concrete case of a five-atomic species (X 2 P u state of the C À 5 ion) [26]. The present study represents the first ab initio handling of the RT effect in six-atomic molecules.…”

“…The value of 25.16 cm À1 is obtained, similar to that for the X 2 P u state of C À 5 (22 cm À1 , as used in Ref. [26]). This parameter, together with those given in Eq.…”

“…The bending potential surfaces are computed at the bond lengths kept fixed at these values. According to our experience with four-and five-atomic molecules [19][20][21][22][23]26], we found it sensible to calculate only 13 points (for each of the components of the X 2 P u state, 1 2 A 0 and 1 2 A 00 ) determining the bending surface, all of them corresponding to planar nuclear arrangements (C s point group). Indeed, we have explicitly shown in our previous studies on the X 2 P u state of B 2 H þ 2 and the X 2 P state of HCCS (see, e.g.…”