The Basis Set Convergence of Spin-Spin Coupling Constants Calculated by Density Functional Methods.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Density functional theory (DFT) is widely used for electronic structure calculations.
• Accurate calculation of nuclear spin-spin coupling constants (NCSCs) is crucial for molecular structure elucidation.
• Existing polarization-consistent basis sets require optimization for NCSCs.

Purpose of the Study:

• To evaluate polarization-consistent basis sets for calculating indirect nuclear spin-spin coupling constants.
• To develop an optimized basis set for DFT calculations of NCSCs.
• To propose a standard set of tight functions for improved basis set convergence.

Main Methods:

• Systematic evaluation of polarization-consistent basis sets for NCSCs.
• Inclusion of tight functions with large exponents to improve basis set convergence.
• Optimization of tight function exponents based on the absolute sum of coupling constant contributions.
• Testing across various molecular systems.

Main Results:

• Convergence of NCSC calculations can be significantly improved by adding tight functions.
• Specific function types (s, p, d, f) are required for different NCSC contributions (Fermi-contact, spin-orbit, spin-dipolar).
• A standard set of tight functions was determined and incorporated into the pcJ-n basis sets.
• The pcJ-n basis sets demonstrate suitability for NCSC calculations with DFT methods.

Conclusions:

• The proposed pcJ-n basis sets offer an efficient and accurate approach for calculating NCSCs using DFT.
• These basis sets provide a reliable tool for chemists investigating molecular structures and properties.
• The study highlights the importance of basis set augmentation for specific quantum chemical properties.