I am not sure how this question is related to this forum. I have a Fortran code. I would like to
1.1) load PSI4 to calculated integrals
1.2) use these integrals in Fortran.
I can try to
2.1) use Fortran to system call a python code
2.2) in that python code, use PSI4 to write integrals into a file
3.3) use Fortran to read the file of integrals
I am not sure if I will spend a lot of time in system call and/or reading/writing files. The interaction between Fortran code and PSI4 is iteratively. Time is a concern.
Is there any more efficient approach? E.g., Fortran to system call PSI4, then read PSI4 integrals to skip reading/writing file, and/or skip system call python; or use some Fortran integral library to compute integrals and everything inside Fortran.
The system is less than 10 main group atoms (most are hydrogens) with double/triple zeta basis functions. I think they can be stored in memory.
Thank you very much