Reparameterization of the chemical-potential equalization model with DFTB3: A practical balance between accuracy and...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• The third-order density-functional tight-binding method (DFTB3) with chemical-potential equalization (CPE) was previously parameterized for organic and biological elements.
• Existing DFTB3/CPE models showed improvements in molecular polarizabilities and intermolecular interactions based on equilibrium structures.

Purpose of the Study:

• To address limitations in existing DFTB3/CPE models, specifically numerical instability in molecular dynamics (MD) simulations and spurious short-distance interactions.
• To develop new, improved DFTB3/CPE models with enhanced stability and accuracy for non-covalent interactions.

Main Methods:

• A simplified parameterization strategy was developed, reducing free parameters to four global ones.
• Two new models, DFTB3/CPE(r) and DFTB3/CPE(r†), were parameterized using the new strategy.
• The performance of the new models was evaluated through molecular dynamics simulations and analysis of potential energy surfaces.

Main Results:

• The new DFTB3/CPE models exhibit smooth potential energy surfaces, enabling stable MD simulations.
• Spurious interactions at short distances were alleviated in the new models.
• Consistent improvements were observed for both neutral and ionic hydrogen bonds.

Conclusions:

• The developed DFTB3/CPE models offer significant improvements over previous versions, enhancing the reliability of simulations for non-covalent interactions.
• The simplified parameterization strategy leads to more robust and accurate computational models for studying molecular systems.
• These advancements are crucial for accurate modeling of organic and biological molecules in computational chemistry.