Minimal Basis Set Hartree–Fock Corrected with Atom-Centered Potentials for Molecular Crystal Modeling and Crystal Structure Prediction

Crystal structure prediction (CSP), determining the experimentally
observable structure of a molecular crystal from the molecular diagram,
is an important challenge with technologically relevant applications
in materials manufacturing and drug design. For the purpose of screening
the randomly generated candidate crystal structures, CSP protocols
require energy ranking methods that are fast and can accurately capture
the small energy differences between molecular crystals. In addition,
a good ranking method should also produce accurate equilibrium geometries,
both intramolecular and intermolecular. In this article, we explore
the combination of minimal-basis-set Hartree–Fock (HF) with
atom-centered potentials (ACPs) as a method for modeling the structure
and energetics of molecular crystals. The ACPs are developed for the
H, C, N, and O atoms and fitted to a set of reference data at the
B86bPBE-XDM level in order to mitigate basis-set incompleteness and
missing correlation. In particular, ACPs are developed in combination
with two methods: HF-D3/MINIs and HF-3c. The application of ACPs greatly
improves the performance of HF-D3/MINIs for lattice energies, crystal
energy differences, energy-volume and energy-strain relations, and
crystal geometries. In the case of HF-3c, the improvement in the crystal
energy differences is much smaller than in HF-D3/MINIs, but lattice
energies and particularly crystal geometries are considerably better
when ACPs are used. The resulting methods may be useful for CSP but
also for quick calculation of molecular crystal lattice energies and
geometries.