A Benchmark and Basis-Set Extrapolation Study of Hyperfine Coupling Constants from the Random Phase Approximation and...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Accurate computation of hyperfine coupling constants (HFCCs) is crucial for linking theoretical predictions with experimental data.
• Current high-accuracy methods for HFCCs are often computationally expensive, limiting their application.
• Developing cost-effective and accurate computational methods for HFCCs is an ongoing challenge.

Purpose of the Study:

• To present and evaluate the theory for calculating HFCCs using σ-functionals.
• To compare the accuracy and computational cost of σ-functionals against established high-accuracy methods.
• To investigate the impact of atomic-orbital basis sets on HFCC calculations and enable systematic extrapolations.

Main Methods:

• Implementation of HFCC calculations using σ-functionals.
• Comparison of σ-functional results with coupled-cluster singles doubles and perturbative triples (CCSD(T)) and domain-based local pair-natural orbital coupled-cluster singles doubles (DLPNO-CCSD) benchmarks.
• Assessment of different atomic-orbital basis sets (pcH, pcJ) and their suitability for HFCC computations.
• Systematic complete basis-set (CBS) extrapolations for HFCCs.

Main Results:

• The best-performing σ-functional achieves accuracy comparable to DLPNO-CCSD for HFCCs.
• σ-functionals offer significantly reduced computational demand compared to DLPNO-CCSD.
• The pcH and pcJ basis-set families are well-suited for RPA, σ-functional, and CCSD(T) HFCC calculations.
• Basis-set extrapolated CCSD(T) HFCCs provide reliable reference values.

Conclusions:

• σ-functionals represent a promising and computationally efficient approach for accurate HFCC calculations.
• The developed methods and basis-set recommendations facilitate reliable HFCC benchmarks.
• This work provides new reference values for HFCCs, aiding future theoretical and experimental studies.