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

TL;DR

This study evaluates the efficiency and accuracy of composite method approximations with locally dense basis sets for calculating NMR shielding constants, providing practical recommendations for different accuracy and computational cost levels.

Contribution

It introduces effective LDBS partition schemes and assesses a wide range of methods, including composite approaches, for NMR shielding calculations.

Findings

pcSseg-n basis sets match pcS-n accuracy for n ≥ 1

Two effective LDBS partition schemes identified

99 methods evaluated for accuracy and efficiency

Abstract

This paper presents a systematic study of applying composite method approximations with locally dense basis sets (LDBS) to efficiently calculate NMR shielding constants in small and medium-sized molecules. The pcSseg-n series of basis sets are shown to have similar accuracy to the pcS-n series when n $\geq1$ and can slightly reduce compute costs. We identify two different LDBS partition schemes that perform very effectively for density functional calculations. We select a large subset of the recent NS372 database containing 290 H, C, N, and O shielding values evaluated by reference methods on 106 molecules to carefully assess methods of the high, medium, and low compute costs to make practical recommendations. Our assessment covers conventional electronic structure methods (DFT and wavefunction) with global basis calculations, as well as their use in one of the satisfactory LDBS approaches, and a range of composite approaches, also with and without LDBS. Altogether 99 methods are evaluated. On this basis, we recommend different methods to reach three different levels of accuracy and time requirements across the four nuclei considered.