A theoretical study of FeCN in the 6Δ electronic ground state

Ab initio molecular orbital study of ground and low-lying electronic states of NiCN

“…[24] which, unlike the r 0 values, can be derived from the observed spectrum in a straightforward manner. As already discussed at length for FeNC, FeCN, and CoCN in our previous papers [1,2,4], we suspect that the discrepancies between the experimentally derived r 0 values and our rovibrationally averaged, theoretical bond length values are caused by neglect of the effects of large-amplitude bending motion in the experimental determination of r 0 . Further details for e X 2 D NiCN will be given in Ref.…”

“…The ab initio methods employed in the present work are quite similar to those used for FeCN [2] and CoCN [3,4], and so only a brief outline is given here.…”

“…We have studied ab initio the first-row transition-metalcontaining isocyanide FeNC [1] and the cyanides FeCN [2] and CoCN [3,4] with a view to investigate the effects of the large-amplitude bending motion and the low-spin/highspin issues [3]. These molecules are basically ionic and can be written as M d+ (CN or NC) dÀ .…”

“…For the triatomic molecules FeNC [1], FeCN [2], CoCN [3,4], and for the diatomic CoH [11], we have studied the electronic structure of the ground electronic states. In addition, for CoCN [3] we have also described the low-lying excited states.…”

“…by perturbation methods and, in the case of the triatomic molecules, by means of the MORBID [12][13][14][15] and RENNER [16][17][18][19] variational approaches. The effects of large-amplitude bending motion have been analyzed for each of the triatomic molecules [1,2,4], and these analyses have demonstrated that several published, experimentally derived r 0 bond lengths for these molecules are of limited physical meaning since they were determined with the effects of large-amplitude bending motion being neglected. We suggest that theoretical, rovibrationally averaged bond lengths, obtained from MORBID or RENNER rovibrational wavefunctions, provide a sounder description of the molecular geometry.…”