Multimode JT Effect

As it will be described in Sect. 5 our analysis of the multimode JT effect is based on the normal-coordinate analysis from the low symmetry points, contrary to the conventional vibronic-coupling theory. Therefore we distinguish between the normal coordinates in the HS conformation, Qnsk, and the normal coordinates in the stable low symmetry (LS) conformation Qjj. 

In this section we present the applications of DFT to discuss JT distortions. The results demonstrate that the computational recipe, described previously. Sect. 3, allows the calculation of the JT parameters, which are in good agreement with the experimental results. In this section, results of the analysis of the multimode JT effect are presented too. 

Ejt = l,463cm ) are considered to be benchmark results for the determination of the JT parameters. They also identitied three dominant normal modes necessary to explain their results. These were recently confirmed by Stanton et al. using Equation-of-motion ionization potential coupled-cluster (EOMIP-CCSD) calculations [45]. Thus, this system is a good test case for both our multideterminental DFT approach in studies of the JT effect and for our model of the analysis of the multimode JT effect. 

Analysis of the Multimode JT Effect at the Stationary Point of Low Symmetry... 

To better visualize the situation, we present in Fig. 2 representative cuts through the PES of the benzene cation (Fig. 2a) as well as the monofluoro derivative (Fig. 2b). A linear combination of the normal coordinates of the JT active modes vg — vg is chosen for the benzene cation and one of the totally symmetric modes for the monofluoro benzene cation. Both are defined to minimize the energy of the conical intersection between the A and C states of the monofluoro derivative, and between the X and B states of the parent cation (within the subspace of JT active coordinates). For the parent cation one identifies a low-energy inter-state curve crossing which is mediated by the multimode JT effect in the two degenerate electronic states. The latter is reflected by the symmetric crossing between the two lowest potential energy curves in Fig. 2a which acmally represents a cut... 

In this paper a new DFT based method for the qualitative and quantitative analysis of the adiabatic potential energy surfaces of JT active molecules is presented. It is shown how DFT can be successfully applied for the calculation of the JT parameters, and thus be a useful tool in understanding the JT effect and related phenomena. The performance of the model has been evaluated for tetrachlorovanadium(IV) (VCI4), an example of ideal, single mode problem cyclopentadienyl radical (C5H5) and bis(cyclopentadienyl)cobalt(II) (cobaltocene, CoCpi) as examples of the multimode problems. The JT parameters obtained using DFT are in excellent agreement with... 

In this section we will investigate the different adiabatic surfaces for electronic orbital doublets and triplets. The treatment is limited to so-called ideal JT systems, i.e. systems with only one JT active mode for each allowed symmetry representation of [Tf - Ai. Although non-ideal or multimode JT problems give rise to more complicated surfaces, it is interesting to note that their extremal properties are similar to those of the corresponding ideal problems [22], Hence as far as the applicability of the epikernel principle is concerned, the neglect of the multimode effect is not expected to affect the conclusions of the present treatment. 

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