Near-Molecular Hartree—Fock Wavefunction for CH3+

Abstract

Ab initio LCAO MO SCF calculations have been performed on CH3+ with a C–H bond length of 1.95 Bohr a.u., using Gaussian-type functions (GTF) as the basis set. By successive increases in the size of the basis set (N) of GTF's (N=12, 20, 28, 36, 40) it was possible to approach the molecular Hartree—Fock limit within 0.03 Hartree a.u. The best calculated total energy was −39.21726 hartrees while the Hartree—Fock limit has been estimated to be −39.243 hartrees for the above C–H distance. The variation of the geometry of CH3+ indicated that the molecule is planar in its ground state and has an extensive electron delocalization. The charge distribution was such that there was approximately 0.13 positive charge on the carbon atom and 0.29 positive charge on each of the three hydrogen atoms. Due to its symmetry, the planar molecule possessed zero dipole moment but it assumed finite values in pyramidal conformations. The total electron density as well as the near Hartree—Fock molecular orbital densities are presented in the form of contour maps. Within the framework of a single Slater determinantal wavefunction, estimations for some of the low-lying electronic excited states of CH3+ have been made.