Treatment of hydrogen bonding in SINDO1

For the treatment of hydrogen bonding in SINDO1, 2p orbitals are introduced on hydrogen. The optimization of the orbital exponent together with the generation of approximate formulas for the core attraction integrals is sufficient to obtain good geometries and binding energies in hydrogen bonded systems. The method is applied to the dimers (H2O)2, (NH3)2, (HF)2, (HCOOH)2, (HCN)2, (H2S)2, and (HCI)2, mixed dimers NH3 · H2O and H2O · HCN, and cyclic polymers (HF)n(n = 3, 4, 6).