Description of halogen bonding in semiempirical quantum-mechanical and self-consistent charge density-functional...

Area of Science:

• Computational chemistry
• Quantum chemistry
• Molecular modeling

Background:

• Halogen bonds are crucial non-covalent interactions.
• Accurate computational methods are needed to model these interactions.
• Semiempirical and DFTB methods offer computational efficiency.

Purpose of the Study:

• To evaluate PM6, PM7, and DFTB3 for describing halogen bonds.
• To investigate the accurate calculation of electrostatic potentials and interaction energies.
• To propose a new correction method for DFTB3 to improve halogen bond descriptions.

Main Methods:

• Semiempirical quantum-mechanical methods (PM6, PM7).
• Self-consistent charge density-functional tight-binding (SCC-DFTB) method (DFTB3).
• Calculation of electrostatic potential and interaction energies.
• Modification of d-orbital energies in DFTB3.

Main Results:

• PM6 and PM7 methods adequately describe the σ-hole for halogen bonds.
• DFTB3 captures geometric aspects but underestimates repulsion.
• A modified DFTB3 approach with adjusted d-orbital energies improves interaction energy calculations.
• Simultaneous accurate description of halogen and hydrogen bonds remains difficult.

Conclusions:

• Semiempirical and DFTB methods show promise for modeling halogen bonds.
• DFTB3 requires parameterization adjustments for accurate interaction energy prediction.
• Further development is needed for methods to accurately model both halogen and hydrogen bonds concurrently.