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Dear Prof Lu,
I have a neutral doublet structure (D0) whose first excited state (D1) turns out to be a charge-transfer state, which shows charge-separation (significantly negative charges on specific atoms and positive charges on other atoms). From what I learned, I would need to add diffuse functions to accurately measure the excitation energy.
At the same time, I want to study the D1 state's electronic state, examine molecular orbitals, etc. But I noticed that with diffuse functions used, the alpha-HOMO in the D1 state (alpha-LUMO in the D0 state) is severely broken in shape. Only when I do not add diffuse functions I see excitation to the correctly shaped orbital.
How should I resolve both energy evaluation and accurate wavefunction analysis at the same time?
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You do not need to add diffuse functions for common CT states. Only Rydberg states, and excitation state calculations for negatively charged system, need diffuse functions.
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Thank you for the reply,
If you don’t mind, could you help me understand this in a little more detail? Because I thought that in a charge-transfer state where certain atoms (that received charge) are significantly negatively charged, at least those atoms should need to be treated with diffuse functions.
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Thank you for the reply,
If you don’t mind, could you help me understand this in a little more detail? Because I thought that in a charge-transfer state where certain atoms (that received charge) are significantly negatively charged, at least those atoms should need to be treated with diffuse functions.
CT excitation doesn't necessarily lead to heavily negatively charged atoms. However, when it is indeed true, adding diffuse functions for those atoms may improve result.
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