convert pyscf integrals to mrcc format

Dear developers,

It seems that both mrcc & molpro's modules for calculation of 2e AO integrals & MO integrals are much slower (~3 times slower) than PySCF's (using qcint) for a large basis cv6z, which is kind of a shock to me!

To take advantage of this, I'm considering writing some module to convert PySCF's integral files to mrcc format so that I could restart mrcc based on these integrals. Anyone could give me a hint on how data are organized in mrcc integral files, or there already exists scripts/modules that could do this?

Best,
Bing

Dear Bing,

Thanks for noting this.
Are you sure that all circumstances are identical with PySCF and Molpro/MRCC?
(Most obvious things could be density fitting options and basis sets if DF is used, spatial symmetry, numerical precision of integrals, parallelization, speed of I/O in your system is the integral file is large, question of restricted or unrestricted MOs, etc...)

Could you post a specific, reproducible example (molecule, output, timing, etc)?

Anyway, you can find the requested MRCC integral file format in this forum reply:
www.mrcc.hu/index.php/forum/general-ques...e-general-doubts#436
starting at "To use external MO integrals..."

Best of luck with it,
Peter