Amplitude of molecular orbitals


As you know, inserting fchk file into IQmol provides MO shape. So we can analyze the contribution of each atoms on the specific MO roughly, as IQmol displays various sizes of orbitals with positive or negative signs. In this situation, I’d like to obtain specific amplitude values of MO on the specific atom. When I open fchk file, its structure was so complicated that I couldn’t complete my purpose. Would you resolve my question?

It’s not that complicated, you just need to run a small example so that the .fchk file is small. You should find a block that is clearly labeled as “Alpha MO coefficients” (separately, Beta, for an unrestricted calculation). You can use PRINT_ORBITALS = TRUE to get the same data in the Q-Chem output file, labeled with AO and MO indices, and that will help you figure out the format of the block-printed data in the .fchk file.

I just followed your comment and tested a small molecule with ‘PRINT_ORBITALS’ options. And now I can understand the structure of fchk file.

Thank you, Prof.Herbert! I always appreciate your advice for my questions. :slight_smile: