Yes! it is here sorry haha I made a mistake there I wanted both links.
The idea is that you obtain them through the many body expansion, where you do fragment-monomers, and then you couple them to form dimers, trimers, tetramers. You truncate at a point where you’re confident you won’t affect the energy too much. Usually this is at trimers/tetramers. This captures most of the many-body effects.
There are methods (also coded up into mqc) that do it via electrostatic embedding (FMO, EE-MBE)
source & further reading
fortran-lang.discourse.group — original article
Gauss-Seidel is faster than Jacobi. Or is it?
LAPACK with more pure procedures
Scientists are using artificial intelligence and large language models to rewrite old code in modern languages