The sodium superoxide radical: X̃2A2 and à 2B2 potential energy surfaces

✍ Scribed by David A. Horner; Wesley D. Allen; Attila G. Császár; Henry F. Schaefer III

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 814 KB
• Volume: 186
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(91)90190-k

✦ Synopsis

The two lowest electronic states of NaO, have been studied using ab initio methods, including RHF SCF, CISD, Davidsoncorrected CISD, UHF SCF, UMPZ-UMP4, CASSCF, and CISD based on CASSCF natural orbitals, with basis sets ranging in qualityfmmNa( lls7p/7s5p), 0(9sSpld/5s3pld) toNa(l3slDp2dlf/7s6p2dlf),O( lls7p2dlf/6s4pZdlf), i.e.fromTZtdto TZZP+f+R. Total and relative energies, geometries, vibrational frequencies, and dipole moments of stationary points on the it 2A2 and ii 2B2 surfaces have been determined. A Czv minimum is proposed for 2 *A2 NaOL with r,(O-0) = 1.335 and r,(Na-0) ~2.10 A. The analogous structure for the A *B2 state is predicted to have r,(O-0) = 1.34 and r,(Na-0) = 2.13 A with an adiabatic excitation energy of r,= 8.5 kcal mol-'. Linear, *II NaOO, which correlates to the 2A2 and 2B2 minima via C, transition states, is predicted to be a shallow minimum lying 17 kcal mol-' above the 2 *A2 structure but with a barrier to rearrangement of less than 1 kcal mol-I. The dissociation energy of the ground state of NaOz is deduced to be Do=38 kcal mol-'. a value substantially lower than recent experimental estimates.