ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Geometric and vibrational characterization of CCN(X˜ 2Π,a˜ 4Σ−,A˜ 2Δ,B˜ 2Σ−,C˜ 2Σ+), CNC(X˜ 2Πg,A˜ 2Δu,B˜ 2Σu−), CNN(X˜ 3Σ−,a˜ 1Δ,b˜ 1Σ+,A˜ 3Π,1 1Π) and NCN(X˜ 3Σg−,a˜ 1Δg,b˜ 1Σg+,A˜ 3Πu) systems have been done using full-valence complete active space SCF (CASSCF) method. The Renner–Teller interaction parameter, ε, is calculated for Π electronic states with CASSCF potentials. Excitation energies with zero-point corrections, T0, electric field gradient (efg), and dipole moment, μ, are calculated using CASSCF, complete active space second order perturbation theory (CASPT2) and multireference singles and doubles configuration interaction (MRD-CI) levels of theory. The fact that CASSCF values of the principal components VXX, VYY, and VZZ of the efg tensor listed through two quantities eq1(=VZZ) and eq2(=VXX−VYY) are not very different from their CASPT2 counterparts, suggests that second-order perturbation involving all singles and doubles over the one-dimensional space spanned by the CASSCF wave function are not important for the efg and μ. However, the important contributions come from the higher excitations (triple, quadruples, etc.), which are included in MRD-CI wave function, by taking multireference zeroth-order wave function. The use of iterative natural orbital seems to be necessary to obtain stable values of the efg and μ in the MRD-CI method. © 2001 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1333701
Permalink
