Extended Conductor-like Polarizable Continuum Solvation Model (CPCM-X) for Semiempirical Methods

We have developed a new method to accurately account
for solvation
effects in semiempirical quantum mechanics based on a polarizable
continuum model (PCM). The extended conductor-like polarizable continuum
model (CPCM-X) incorporates a computationally efficient domain decomposition
conductor-like screening model (ddCOSMO) for extended tight binding
(xTB) methods and uses a post-processing approach based on established
solvation models, like the conductor-like screening model for real
solvents (COSMO-RS) and the universal solvent model based on solute
electron density (SMD). According to various benchmarks, the approach
performs well across a broad range of systems and applications, including
hydration free energies, non-aqueous solvation free energies, and
large supramolecular association reactions of neutral and charged
species. Our method for computing solvation free energies is much
more accurate than the current methods in the xtb program package.
It improves the accuracy of solvation free energies by up to 40% for
larger supramolecular association reactions to match even the accuracy
of higher-level DFT-based solvation models like COSMO-RS and SMD while
being computationally more than 2 orders of magnitude faster. The
proposed method and the underlying ddCOSMO model are readily available
for a wide variety of solvents and are accessible in xtb for use in
various computational applications.