First, optimaze the groud state of the molecule. If you are looking for vertical transition energy, then you need to calculate single point energy using optimized geometry of the ground srtate: td b3lyp/6-31g* density=current. This means that I request time dependent B3LYP implementation, the energies of the three lowest excited states will be printed, CI density of the first exited state will be used for the properties calculation. Δμ between the ground and the first excited state is the difference between dipole moments of the ground state and excited state calculations. Important to use "density=currenr" or density=all, otherwise scf density is used in the properties calculations. If you are interested in different excited state you need to resquest it explicitely. For example td(nstates=10,root=5) means that you requeste 10 lowest excited states and the state # 5 is your state of interest. If you want to get adiabatic excitation energies you need to optimize first your state of interest: opt td(nstates=10,root=5), You can also use other methods for excited state calculatiuons; CIS, CASSCF, SAC-CI, EOM-CCSD, All of them except for CIS are much more computationally expensive than TD-DFT
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