Nonbonded potential function models for crystalline oxohydrocarbons

Nonbonded O^...O potential parameters of the (exp - 6) type were derived from five selected oxohydrocarbon crystal structures, which do not have hydrogen bonds: β-oxygen, carbon dioxide (CO₂), trioxane (C₃H₆O₃), tetroxocane (C₄H₈O₄) and succinic anhydride (C₄H₄O₃). Previously established hydrocarbon H and C nonbonded parameters were transferred. Net atomic charges were calculated separately by obtaining a least-squares fit to the molecular electric field calculated by the ab initio self-consistent-field molecular-orbital method. The resulting O^...O nonbonded potential was found to transfer well to the structures of pentoxecane (C₅H₁₀O₅), 1,4- cyclohexanedione (C₆H₈O₂) and diglycolic anhydride (C₄H₄O₄). The potential did not transfer well to the structures of p-benzoquinone (C₆H₄O₂) and furan (C₄H₄O). The addition of an approximate weak hydrogen-bonding potential for a C-H^... O hydrogen bond improved the fit to the latter two structures.