Molcas Forum

abid

Member

Registered: 2015-11-12

Posts: 41

Open Shell/UHF based calculations

Dear All
I am performing some calculations on a system. I am surprised by the energy difference provided by MOLCAS for open shell.
I have an experimental result and also performed ORCA based calculations.
I suspect the energies provided by MOLCAS are not correct for open shell system. Here I try an example to put my question in some reasonable way.
I performed calculations to simulate the absorption spectra of H2S and HS-radical. The energy difference between both of peaks at sulphur K-edge are at 2476 and 2469 eV as provided by MOLCAS. the strange thing is that experimental results suggest
that they should be at 2471 and 2469 eV. By applying the shift of 5 eV to MOLCAS results peaks will be at 2471 and 2464 eV. Orca predicted values for this system are 2471 and 2468.8 eV pretty near to experimental values. I would like to ask for any suggestion to improve the caspt2 based energies obtained by molcas. I have tried almost every option.

Any guidance will be highly appreciated
Thanks a lot in advance