CASSCF, CASPT2, AND MRCI INVESTIGATIONS OF FORMYLOXYL RADICAL (HCOO.)

Citation
A. Rauk et al., CASSCF, CASPT2, AND MRCI INVESTIGATIONS OF FORMYLOXYL RADICAL (HCOO.), Chemical physics, 197(1), 1995, pp. 73-80
Citations number
29
Categorie Soggetti
Physics, Atomic, Molecular & Chemical
Journal title
ISSN journal
03010104
Volume
197
Issue
1
Year of publication
1995
Pages
73 - 80
Database
ISI
SICI code
0301-0104(1995)197:1<73:CCAMIO>2.0.ZU;2-E
Abstract
The structures of the electronic states of HCOO. were optimized at CAS SCF and CASPT2 levels of theory with generally contracted basis sets o f atomic natural orbital type: [8s4p]/[3s2p] for hydrogen and [14s9p4d ]/[4s3p2d] for carbon and oxygen atoms. Vibrational frequencies were c alculated to verify the characteristics for some of the optimized stat ionary points. MRCI calculations were carried out for the a radicals a t the CASPT2 optimized geometries to provide a test on the higher-orde r correlation effects. At the CASPT2, level, the lowest electronic sta te of HCOO. is the (2)A(1) state. The electronic energy of the B-2(2) state is 6 kJ/mol above. The broken symmetry (2)A' state is predicted to lie 25 kJ/mol above the (2)A(1) State and to be a transition struct ure for rearrangement to HOCO.. Single-point MRCI calculations field t he reverse order for the C-2v symmetric states, (2)A(1) state being pr edicted to be 9.5 kJ/mol above the B-2(2) state. The (2)A' state is ne arly degenerate with the (2)A(1) state. Relative energies predicted at the (unoptimized) MRCI level are almost identical to those found by s ingle-reference CI calculations.