First optimize the molecule then compute electronic transitions and finally check the difference between the eigen values of LUMO and the HOMO. (Energy difference will be in Hatree).
First optimize the molecule then compute electronic transitions and finally check the difference between the eigen values of LUMO and the HOMO. (Energy difference will be in Hatree).
If you need only energies, then geometry optimization calculation will be enough. Can you send a picture of results with orbitals? It seems that you deal with odd number of electrons in the system.
First you optimized molecules and followed calculate energy. for Example Energy-DFT-B3LYP. The out file open, then right click, then chose MOs and and get HOMO and LUMO Energy values.