I’m trying to do EOM-CC3 calculations for the benzene molecule (input and output are attached), but the CC3 code calculates the correction (from EOM-CCSD) for just one state. I want to calculate the CC3 correction for all roots. Can I fix this? Or does the code calculate one correction at a time?
In addition, does the psi4 code have another approximation instead of CC3 for triples correction in excited states?
Alan Guilherme Falkowski.
benzene.dat (834 Bytes)
benzene_output.dat (36.2 KB)
The nature of CC3 forces the algorithm to compute one root at a time because we must avoid storing triple excitation vectors. CC3 is the only excited-state triples method in Psi4.
Thank you, @crawdad.
How can I select the root to do de CC3 calculation?
In the input that I attached, the code calculate the correction for the last B3u state.
The EOM code first finds the number of EOM-CCSD roots requested and then, by default, uses the last state in the current irrep to follow for the CC3 correction.
If you wish to compute the CC3 energy for a state that is not the highest energy state computed with EOM CCSD, you should be able to select it with the “PROP_ROOT” keyword. Occasionally this is helpful for convergence of the EOM CCSD or convenient to be able to see what states are just higher.
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