Indirect NMR spin-spin coupling constants in diatomic alkali halides

Area of Science:

• Physical Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Nuclear Magnetic Resonance (NMR) spectroscopy is crucial for determining molecular structure.
• Accurate calculation of NMR spin-spin coupling constants (SSCCs) is essential for interpreting experimental data.
• Alkali halides present unique challenges for computational chemistry due to significant relativistic effects.

Purpose of the Study:

• To accurately compute NMR spin-spin coupling constants for diatomic alkali halides (MX).
• To evaluate the performance of various computational methods, including relativistic corrections, for predicting SSCCs.
• To provide a reliable theoretical benchmark for experimental studies of alkali halides.

Main Methods:

• Calculated non-relativistic coupled-cluster singles-and-doubles (CCSD) values.
• Incorporated relativistic corrections using four-component density-functional theory (DFT) with the PBE0 functional (50% exact-exchange).
• Applied rovibrational corrections estimated from literature data.

Main Results:

• The combined CCSD and relativistic DFT approach yielded SSCCs in superior agreement with experimental data compared to standard relativistic DFT methods.
• The PBE0 functional with 50% exact-exchange provided better results than with 25% exact-exchange.
• Rovibrational corrections further enhanced the agreement between theoretical and experimental values.

Conclusions:

• The developed computational strategy accurately predicts NMR spin-spin coupling constants for diatomic alkali halides.
• Relativistic effects and rovibrational contributions are critical for high-accuracy SSCC calculations in these systems.
• This work offers a robust theoretical framework for studying similar systems in chemical physics and spectroscopy.