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

We have developed a new method to accurately accountfor solvationeffects in semiempirical quantum mechanics based on a polarizablecontinuum model (PCM). The extended conductor-like polarizable continuummodel (CPCM-X) incorporates a computationally efficient domain decompositionconductor-like screening model (ddCOSMO) for extended tight binding(xTB) methods and uses a post-processing approach based on establishedsolvation models, like the conductor-like screening model for realsolvents (COSMO-RS) and the universal solvent model based on soluteelectron density (SMD). According to various benchmarks, the approachperforms well across a broad range of systems and applications, includinghydration free energies, non-aqueous solvation free energies, andlarge supramolecular association reactions of neutral and chargedspecies. Our method for computing solvation free energies is muchmore accurate than the current methods in the xtb program package.It improves the accuracy of solvation free energies by up to 40% forlarger supramolecular association reactions to match even the accuracyof higher-level DFT-based solvation models like COSMO-RS and SMD whilebeing computationally more than 2 orders of magnitude faster. Theproposed method and the underlying ddCOSMO model are readily availablefor a wide variety of solvents and are accessible in xtb for use invarious computational applications.

Automated summary

We have developed a new method, named CPCM-X, to accurately account for solvation effects in semiempirical quantum mechanics. This method combines the computationally efficient ddCOSMO model with established solvation models like COSMO-RS and SMD, and improves the accuracy of solvation free energies by up to 40% for large supramolecular association reactions. The proposed method is more accurate and more than 2 orders of magnitude faster than the current methods in the xtb program package.