MO guess from other program

Dear Prof. Kallay,

I would like to learn the possibility to generate or read SCF initial guess from other program. We are doing a radical system and its SCF wavefunction is very difficult to converge. If I have already got a converged UHF wavefunction from other programs using orbital rotation, and have printed out the MO coefficients, is there a possibility to format those coefficients into the format that MRCC can read, then either feed it as the initial guess for UHF calculation using MRCC, or just proceed to the post-HF calculations?

I checked the MOCOEF file generated after MRCC calculation that could be used with scfiguess=mo in the next calculation, however, that file seems to be a binary file and I don't know how to deal with it.

Thank you in advance for your kind response.

Sincerely,
Jen-Shiang
(Kenny)

Dear Jen-Shiang,
It is a complicated task. First, you should take into account that the order of AOs in the two programs are probably different, and you should permute the MO coefficients accordingly. To get the ordering used in mrcc set verbosity=3, and you will find the order at the beginning of the output. Second, you should write a routine that saves the MO coefficients in the required format. For that purpose you should call the wrtmo from file combin.f. Third, you should run the program with scfiguess=mo. You cannot skip the SCF since the Fock-matrix must be generated.

Dear Prof. Kallay,

Thank you for your explanation. I checked the MOLDEN file and it might be easier to start over there.

There is another question that might or might not related to this. I also saw a MOLDEN.perm file after SCF calculation and it seems that orbital permutation might be possible in MRCC. My question is, can I just permute the orbitals generated from a high-spin calculation then do orbital rotation just like that in MOLPRO, which might be able to converge the UHF calculation for the radicals?

Thanks a lot for your advise.

Jen-Shiang

When you're using MOLPRO anyway, why don't you use the MOLPRO->MRCC interface?

Dear Jen-Shiang,
The MOLDEN.perm file contains the permutation which converts the MO coefficients to the order required by molden.
I don't know exactly what molpro does, but as explained below, you can easily read the MO coefficients and interchange the MOs or rotate them.