1 research outputs found
Effective Fragment Potential Method for H‑Bonding: How To Obtain Parameters for Nonrigid Fragments
Accuracy of the effective
fragment potential (EFP) method was explored
for describing intermolecular interaction energies in three dimers
with strong H-bonded interactions, formic acid, formamide, and formamidine
dimers, which are a part of HBC6 database of noncovalent interactions.
Monomer geometries in these dimers change significantly as a function
of intermonomer separation. Several EFP schemes were considered, in
which fragment parameters were prepared for a fragment in its gas-phase
geometry or recomputed for each unique fragment geometry. Additionally,
a scheme in which gas-phase fragment parameters are shifted according
to relaxed fragment geometries is introduced and tested. EFP data
are compared against the coupled cluster with single, double, and
perturbative triple excitations (CCSDÂ(T)) method in a complete basis
set (CBS) and the symmetry adapted perturbation theory (SAPT). All
considered EFP schemes provide a good agreement with CCSDÂ(T)/CBS for
binding energies at equilibrium separations, with discrepancies not
exceeding 2 kcal/mol. However, only the schemes that utilize relaxed
fragment geometries remain qualitatively correct at shorter than equilibrium
intermolecular distances. The EFP scheme with shifted parameters behaves
quantitatively similar to the scheme in which parameters are recomputed
for each monomer geometry and thus is recommended as a computationally
efficient approach for large-scale EFP simulations of flexible systems