Correlated calculation of the interaction in the nitromethane dimer

The interaction energy of the nitromethane dimer at several separations between the monomers was calculated using fourth-order many-body perturbation theory (MBPT), with single, double, and quadruple (SDQ) excitations included. The self-consistent field (SCF) counterpoise (CP) correction, and second-order dispersion energy were also computed. A double-zeta plus polarization basis was used. The monomers were oriented so that a hydrogen atom on each monomer could form a hydrogen bond with an oxygen on the other monomer. An interaction energy of 3.57 and 5.04 kcal/mol was found at the SCF and SDQ-MBPT(4) levels of theory, respectively. The CP-corrected SCF energy added to the second-order dispersion energy gives an interaction energy of 5.62 kcal/mol.