Analytic energy gradients in combined second order Moller-Plesset perturbation theory and conductorlike polarizable continuum model calculation

The analytic energy gradients in combined second order Moller-Plesset perturbation theory and conductorlike polarizable continuum model calculations are derived and implemented for spin-restricted closed shell (RMP2), Z-averaged spin-restricted open shell (ZAPT2), and spin-unrestricted open shell (UMP2) cases. Using these methods, the geometries of the S-0 ground state and the T-1 state of three nucleobase pairs (guanine-cytosine, adenine-thymine, and adenine-uracil) in the gas phase and aqueous solution phase are optimized. It is found that in both the gas phase and the aqueous solution phase the hydrogen bonds in the T-1 state pairs are weakened by similar to 1 kcal/mol as compared to those in the S-0 state pairs. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3649947]