LCGTO‐LSD calculations for CH2

LCGTO‐LSD calculations for ground (3B1) and excited (1A1) states of methylene, CH2, have been performed. Various exchange‐correlation potentials and a variety of basis sets (including f functions) have been used. For both states the LSD optimized geometry agrees well with both experimental and the most advanced ab initio results. The correct ground state is found, and the 1A1‐3B1 energy separation was found to be ∼ 15 kcal/mol, using the “best” local exchange‐correlation potential (VWN), the experimental value being ∼ 9 kcal/mol. This result compares favorably with the Hartree‐Fock limit separation of 25 kcal/mol. The Kohn‐Sham exchange potential leads to a gap of ∼26 kcal/mol.