Dispersion-Corrected DFT Methods for Applications in Nuclear Magnetic Resonance Crystallography

Area of Science:

• Computational Chemistry
• Solid-State Physics
• Crystallography

Background:

• Nuclear electric field gradient (EFG) tensor parameters are sensitive to electronic structure.
• Accurate calculation of EFG tensors aids in predicting, refining, and optimizing crystal structures.

Purpose of the Study:

• To optimize Grimme (D2) and Tkatchenko-Scheffler (TS) atomic-pairwise force field dispersion corrections using plane-wave density functional theory (DFT) calculations.
• To evaluate the impact of these optimized force fields on the accuracy of calculated EFG tensors and crystal structures.

Main Methods:

• Plane-wave density functional theory (DFT) calculations were employed to compute EFG tensors.
• Optimized Grimme (D2) and Tkatchenko-Scheffler (TS) dispersion corrections were applied to organic solids.
• Calculated EFG tensors for ¹⁴N, ¹⁷O, and ³⁵Cl were compared against experimental data for 95 materials.

Main Results:

• Refined force fields led to improved representations of true crystal structures.
• Calculations of ³⁵Cl EFG tensors showed remarkable agreement with experimental values, particularly for chloride ions involved in H···Cl^- hydrogen bonds.
• Optimized structures exhibited atomic coordinates more closely resembling those from neutron diffraction.

Conclusions:

• Optimized dispersion corrections enhance the accuracy of DFT calculations for crystal structure refinement and EFG tensor prediction.
• These methods improve the modeling of hydrogen bonding, crucial for accurate structural analysis.
• The refined protocols are valuable for nuclear magnetic resonance (NMR) crystallography and related research fields.