Description of non-covalent interactions in SCC-DFTB methods

Area of Science:

• Computational chemistry
• Quantum chemistry

Background:

• The self-consistent charges density functional tight binding (SCC-DFTB) method offers a computationally efficient approach for electronic structure calculations.
• Accurate description of non-covalent interactions, crucial for molecular modeling, remains a challenge for SCC-DFTB.
• Existing SCC-DFTB variants struggle with the precise quantification of hydrogen bonding and London dispersion forces.

Purpose of the Study:

• To analyze and enhance the description of non-covalent interactions within various SCC-DFTB methodologies.
• To identify and quantify the sources of error in SCC-DFTB's treatment of electrostatic and polarization contributions to interaction energies.
• To develop and validate improved correction schemes for SCC-DFTB, particularly for hydrogen bonding and dispersion.

Main Methods:

• Evaluation of multiple SCC-DFTB variants for their ability to model non-covalent interactions.
• Implementation of an interaction energy decomposition scheme to pinpoint errors in electrostatic and polarization terms.
• Application and reparameterization of empirical dispersion corrections (D3H4) for enhanced accuracy.
• Testing the compatibility of corrections with third-order SCC-DFTB and the 3OB parameter set.

Main Results:

• London dispersion interactions can be effectively improved using empirical corrections.
• Hydrogen bonding description in SCC-DFTB is significantly limited by the monopole approximation and minimal basis sets, underestimating electrostatic and polarization terms.
• SCC-DFTB combined with empirical D3H4 corrections demonstrated superior performance among the tested methods.
• Reparameterization of D3H4 corrections ensures compatibility with the latest third-order SCC-DFTB (3OB parameter set).

Conclusions:

• Empirical corrections, specifically D3H4, are vital for improving the accuracy of non-covalent interactions in SCC-DFTB.
• The monopole approximation and minimal basis sets in SCC-DFTB necessitate corrections for accurate electrostatic and polarization descriptions.
• Reparameterized D3H4 corrections offer a robust solution for enhancing SCC-DFTB's predictive power in modeling non-covalent interactions.