Electronic excitation energy calculation by the fragment molecular orbital method with three-body effects

A scheme for full quantum electronic excited state calculation is proposed that is based on the fragment molecular orbital (FMO) method with three-body effects. The accuracy and efficiency of this scheme is checked by calculating the excitation energy of hydrated formaldehyde and hydrated phenol. In all cases, three-body effects improved the excitation energy by the one- and two-body FMO methods with small computational cost, and the excitation energy approached more closely the full calculation value. The results also show that the three-body effects were relatively large and cannot be neglected.