From HOMO-LUMO values, I found energy gap (Elumo - Ehomo) to be 0.20322, which seems to be fine and also homo is more stable than lumo.
But I am confused if the value obtained for E(lumo) is correct or not, as I observed negative values for both Ehomo and Elumo in journal papers. So, could one please help me clarify it? or guide me to any relevant resource material for understanding these results.
Hi Prince Kumar Baranwal
Actually, LUMO orbital do not optimize in optimization processing. A suitable method in order to reduce of error in energy is three approach point (TAP) methods. This method approximately calculate energies.
IP (ionization potential)= E(cation)-E(natural)=E(HOMO)
EA(electron affinity)=E(anion)-E(natural)=E(LUMO)
There is more detail in R. G. Parr books (Density functional theory of atom and molecules)
Best regards
" EA(electron affinity)=E(LUMO)" is extended version of Koopmans' theorem, that actually quite approximate in a lot of cases.
However, if one is ready for speculations - he can say that positive value for LUMO mean that attachment of electron to given molecule is energetically unfavourable.(nevertheless this does not mean that process can not happen).
Thank you all very much Dmitry Sharapa Fazlolah Eshghi Saravanan Chinnusamy
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