Efficient Calculation of NMR Shielding Constants Using Composite Method Approximations and Locally Dense Basis Sets

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Accurate calculation of Nuclear Magnetic Resonance (NMR) shielding constants is crucial for molecular structure elucidation.
• Traditional methods often face high computational costs, limiting their application to larger systems.
• Locally Dense Basis Sets (LDBS) offer a promising approach to improve computational efficiency.

Purpose of the Study:

• To systematically evaluate composite method approximations combined with LDBS for calculating NMR shielding constants.
• To compare the performance of different LDBS partition schemes, particularly for density functional theory (DFT) calculations.
• To provide practical recommendations for selecting computational methods based on desired accuracy and time constraints for H, C, N, and O nuclei.

Main Methods:

• Application of composite method approximations with locally dense basis sets (LDBS).
• Assessment of the pcSseg-n series of basis sets against the pcS-n series.
• Evaluation of two distinct LDBS partition schemes for DFT calculations.
• Benchmarking of 99 different computational methods, including conventional electronic structure methods (DFT, wave function) and composite approaches, with and without LDBS, using the NS372 database.

Main Results:

• The pcSseg-n basis sets demonstrate comparable accuracy to pcS-n (for n ≥ 1) with reduced computational expense.
• Two LDBS partition schemes were identified as highly effective for DFT calculations.
• A comprehensive assessment of 99 methods revealed varying performance levels across different accuracy and computational cost requirements.

Conclusions:

• Composite methods combined with LDBS provide an efficient route for calculating NMR shielding constants.
• The pcSseg-n basis sets represent a viable, cost-effective alternative to pcS-n.
• Tailored recommendations are provided for selecting NMR shielding calculation methods based on specific accuracy and resource limitations for key nuclei.