My system has 52 atoms, and I intend to calculate SAPT at the levels sSAPT0/jun-cc-pVDZ, SAPT2+/aug-cc-pVDZ and SAPT2+(3)dmp2/aug-cc-pVTZ to obtain the Lennard-Jones parameters for the atoms of this molecule.
Given my little experience in SAPT, could I ask a few questions?
1 - Is calculating the SAPT energy of a system of this size (i.e., 52 atoms) something viable or is the computation time too high? I say this because I would have to calculate the energy for several pairs of hexamethyldisiloxane for my purpose. Did any colleague calculate the energy of a system similar to this size and could share the estimated time spent on the calculation?
2 - What would be a good starting guess for the number of processors that I could use to calculate SAPT for a system of this size (i.e., 52 atoms)?
The system size is routinely accessible with SAPT2+(3) and TZ basis with psi4.
I’d recommend jun-cc-pVTZ instead of the full aug-cc-pVTZ, the heavy augmentation is not needed for accurate results. Especially on the H atoms. This will save a lot of basis functions.
The scaling beyond say 16 threads is not good but still worth it if the node is free. Running multiple SAPT2+(3) on a single node will slow things down because disk writing/reading may limit the calculations.