Nuclear shielding constants by density functional theory with gauge including atomic orbitals

Abstract

Recently, we introduced a new density-functional theory ͑DFT͒ approach for the calculation of NMR shielding constants. First, a hybrid DFT calculation ͑using 5% exact exchange͒ is performed on the molecule to determine Kohn-Sham orbitals and their energies; second, the constants are determined as in nonhybrid DFT theory, that is, the paramagnetic contribution to the constants is calculated from a noniterative, uncoupled sum-overstates expression. The initial results suggested that this semiempirical DFT approach gives shielding constants in good agreement with the best ab initio and experimental data; in this paper, we further validate this procedure, using London orbitals in the theory, having implemented DFT into the ab initio code DALTON. Calculations on a number of small and medium-sized molecules confirm that our approach produces shieldings in excellent agreement with experiment and the best ab initio results available, demonstrating its potential for the study of shielding constants of large systems.

Density functional theory investigation of3dtransition metal NMR shielding tensors in diamagnetic systems using the gauge-including projector augmented-wave method

“…Other investigations on molecular systems have shown that calculated shielding parameters are highly dependant on the type of XC functionals. [106][107][108][109][110] Linear response of crystalline or molecular orbitals to the magnetic field perturbation are strongly dependant on the occupied-virtual energy gap (E gap ) and the shape of the virtual orbitals, through the first-order corrected wave function (Eq. 14).…”

Quantum-chemical simulation of solid-state NMR spectra: the example of a molecular tweezer host–guest complex

“…For the DFT calculations we employed the BP86(VWN) functional [16][17][18] with the SG-1 grid [19] for the numerical integrations [20]. NMR calculations were performed using the 6-31G * * [21,22] basis with our linear-scaling method [7,8] at the GIAO-HF [23][24][25][26][27] and GIAO-DFT [28][29][30][31][32][33][34] levels, respectively. Relative NMR shifts are given, unless noted otherwise, with respect to those of a TMS molecule calculated at the same level of theory.…”

Structural Characterization of Phosphorus‐Based Networks and Clusters: 31P MAS NMR Spectroscopy and Magnetic Shielding Calculations on Hittorf’s Phosphorus

“…The assignment is supported further by DFTbased ab initio chemical shift calculations using a cluster-model approach, which gives good agreement between experimental and calculated chemical shift values. The 31 P chemical shifts appear to be strongly correlated with the average PÀP bond lengths within the PA C H T U N G T R E N N U N G (P 1/3 ) 3 coordination environments, whereas no clear dependence on average P-P-P bond angles can be detected.…”

“…[6,10] High-resolution magic-angle-spinning (MAS) NMR spectroscopy offers a sensitive differentiation between distinct phosphorus environments based on the extremely wide 31 P chemical shift range (d = 300 to À550 ppm in the case of crystalline phosphides). [6, 10d, 11] Despite this sensitivity, to date only a few promising correlations of 31 P chemical shifts with structural characteristics have been shown.…”