The symmetry breaking problem in the triflouride anion: A multireference approach

Abstract

Articles you may be interested inComment on ''Infrared spectrum and theoretical study of the dinitrogen pentoxide molecule (N2O5) in solid argon'' [A comparison of two approaches to perturbation triple excitation corrections to the coupledcluster singles and doubles method for highspin openshell systemsThe multireference MCSCF and MCSCFϩMP2 methods were applied to the study of the optimum geometry of the F 3 Ϫ anion, its vibrational frequencies and its dissociation energy into F 2 ϩF Ϫ . The system has a strong multireference character. The optimum geometry of the F 3 Ϫ anion doing a MCSCF͑3,4͒ or a MCSCF͑9,16͒ computation presents a symmetry breaking from D ϱh →C ϱv . Using other active spaces, like the one constructed following the orbital doubling technique, the symmetry breaking problem is solved. Finally, the accurate computation of the dissociation energy requires the inclusion of the dynamical correlation: the MCSCF dissociation energy is about 1 3 of the final MCSCFϩMP2 result. The best multireference results obtained here agree very well with the best monoreference results of Heard, Marsden, and Scuseria ͓G. L. Heard, C. J. Marsden, and G. Scuseria, J. Phys. Chem. 96, 4359 ͑1992͔͒ obtained with a QCISD͑T͒ and similar methods.

Structure and Properties of Polyfluoride Fn–Clusters (n= 3–29)

“…The T 2 amplitudes for F 3 and F 3 − are 0.14 and 0.16, respectively, which is in agreement with the previously found multireference character of the F 3 − wave function. 34 Dissociation energies of F 2 and F 2 − have been computed according to the equation …”

A multiconfigurational approach of the symmetry breaking problem in the cyclic C3H radical

“…The CAS(7;7,3) model includes the resonance effect. The orbital doubling technique [18,19] can be used to ensure that the size effect is properly treated. For the CAS(7;7,3) wavefunction, the reference configuration of the active space can be written 5a 2 1 1b 2 1 6a 2 1 3b 1 2 2b 0 1 3b 0 1 4b 0 2 7a 0 1 5b 0 2 8a 0 1 : The valence bond structures ( Fig.…”

“…Specially tailored multireference wavefunctions have been used to restore the delocalization effect [19,24]. Most recent works have employed the convenient CASSCF method, which provide with sufficient latitude to set the true symmetry wavefunction [18,20,22,27]. Another way to obtain a proper electronic wavefunction is the nonorthogonal orbital CI [21,29].…”

“…It has been frequently encountered in open-shell systems with high nuclear symmetry. Numerous quantum chemical investigations have been reported on such systems, among which we find linear molecules such as F À 3 [18] and non-linear molecules whose nuclear frame has the C 2v symmetry (HCO 2 [19][20][21], NO 2 [20,22,23], the triplet states of CO 2 [24], C þ 3 [25]) or the D 3h symmetry (NO 3 [26,27], C 3 H 3 [28]). Within the Hartree-Fock theory, the symmetry breaking has been explained by the competition between two stabilizing contributions, the resonance (or delocalization effect) and the orbital size effect [19].…”

Halogen Bonds in Novel Polyhalogen Monoanions

“…Mota et al. performed MCSCF and MCSCF+MP2 computations of [F 3 ] − and found that dynamical correlation should be considered for the accurate calculation of the binding energy . In general, however, both the MCSCF+MP2 and single‐reference CCSDT results match well with the experimental data obtained in inert‐gas matrices …”