Equilibrium geometry of isocyanomethylene (HCNC) and comparison to the troublesome isomer cyanomethylene (HCCN)

Journal Article · Fri Jul 01 00:00:00 EDT 1994 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.468152· OSTI ID:7049876

Kellogg, C B; Galbraith, J M; Fowler, J E; Schaefer, III, H F ^[1]

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1. Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602 (United States)

Inspired by the recent experimental study of the radical anions HCCN[sup [minus]] and HCNC[sup [minus]] and by earlier examinations of HCCN, the equilibrium geometry of the HCNC molecule has been investigated using both self-consistent field (SCF) and configuration interaction methods including single and double excitations (CISD). The largest basis set used was a triple-[zeta] plus double polarization with diffuse functions and higher angular momentum functions appended to each atom [TZ2P([ital f],[ital d])+diff]. Using this basis, the H--C--N equilibrium angle is predicted to be 128.5[degree] at the CISD level of theory. Additionally, the zero point vibrational energy (ZPVE) corrected energy separation of the bent and linear conformations was predicted to be 10.1 kcal mol[sup [minus]1] at the CISD level of theory with the largest basis set employed. The barrier to linearity is 7.7 kcal mol[sup [minus]1] at the CCSD level of theory and 6.9 kcal mol[sup [minus]1] at the CCSD(T) level of theory, employing the CISD optimized geometries with a basis that was comprised of triple-[zeta] plus double polarization with higher angular momentum functions appended to each atom [TZ2P([ital f],[ital d])]. These results were compared to those obtained in previous [ital ab] [ital initio] investigations of HCCN, which has been dubbed a quasilinear molecule by the most recent experimental investigators. HCNC is predicted to lie 22.2 kcal mol[sup [minus]1] above HCCN at the CISD level of theory, with a the TZ2P([ital f],[ital d]) basis. The differences between the two isomers are discussed and HCNC is predicted to be a definitively bent molecule, rather than quasilinear.

• DOE Contract Number: FG09-87ER13811
• OSTI ID: 7049876
• Journal Information: Journal of Chemical Physics; (United States), Vol. 101:1; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ISOCYANIC ACID
MOLECULAR STRUCTURE
METHYLENE RADICALS
ANIONS
CORRELATIONS
CYANOGEN
EQUILIBRIUM
GROUND STATES
HARMONIC OSCILLATORS
MOLECULAR IONS
TRIPLETS
CARBONIC ACID DERIVATIVES
CHARGED PARTICLES
ELECTRONIC EQUIPMENT
ENERGY LEVELS
EQUIPMENT
IONS
MULTIPLETS
NITROGEN COMPOUNDS
ORGANIC COMPOUNDS
OSCILLATORS
RADICALS
664100* - Theory of Electronic Structure of Atoms & Molecules- (1992-)