Excited state geometry optimizations by time-dependent density functional theory based on the fragment molecular orbital method

The energy gradient method is introduced to the fragment molecular orbital based time-dependent density functional theory (FMO-TDDFT), which we have recently developed to calculate excitation energies of large systems by dividing them into fragments. By using the energy gradient of FMO-TDDFT, excited state geometry optimizations of a polypeptide and solvated formaldehyde are carried out using the LC-BOP functional and the 6-31G∗ basis set. The accuracy of the optimized structures and the excitation energies in comparison to conventional TDDFT is discussed.