Optimization of the explicit polarization (X-Pol) potential using a hybrid density functional.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Electronic Structure Theory

Background:

• The explicit polarization (X-Pol) method is a fragment-based electronic structure theory.
• It localizes molecular orbitals within system fragments.
• Accurate modeling requires accounting for exchange repulsion and dispersion interactions.

Purpose of the Study:

• To incorporate pairwise, empirical Lennard-Jones terms into the X-Pol effective Hamiltonian.
• To optimize these terms for describing interactions between molecular fragments.
• To evaluate the accuracy of the enhanced X-Pol method for hydrogen bonding.

Main Methods:

• The X-Pol potential was constructed using the B3LYP hybrid density functional and the 6-31G(d) basis set.
• Lennard-Jones parameters were optimized using a dataset of 105 bimolecular complexes.
• Performance was assessed by comparing binding energies and hydrogen bond distances with high-level theoretical methods.

Main Results:

• The optimized X-Pol potential accurately describes hydrogen bonding interactions.
• The root mean square deviation for binding energies against CCSD(T)/aug-cc-pVDZ was 0.8 kcal/mol.
• Average deviation in hydrogen bond distances from B3LYP/aug-cc-pVDZ was approximately 0.1 Å.

Conclusions:

• The enhanced X-Pol method with Lennard-Jones terms provides a reliable description of intermolecular interactions.
• This approach offers a computationally efficient way to study large systems.
• The method shows promise for applications in condensed-phase and macromolecular systems.