Comparison of charge transfer energy according to SAPT0 with NBO

Dear Psi4 Community!

Can you please tell me if it is possible to compare the calculated energy of charge transfer according to SAPT0 (-st) with the energy E2 NBO. The trend is following for my systems.
Charge Transfer,/ E2, kcal/mol

1 0.3/ 8.7
2 2.1/ 12.7
3 3.2 / 14.9
Thank you for your attention.

Best regards

In general, no. They are differently defined.
The difficulty lies in the fact that CT is well understood as a chemical concept, but poorly defined as a physical/mathematical term.
Thus CT among EDA schemes is very difficult to compare with each and can even be different by an order of magnitude (I dont find the paper that nicely showed this).

Some starting points for reading:
EDA method overview:
for SAPT vs NBO explicitly:;

1 Like

Dear hokru,
Thanks for the useful information. I also wanted to clarify if the charge transfer can be said to increase from 1 to 3 by referring only to the result SAPT0 (st)

Thank you for your attention.

Best regards

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