Soft experimental constraints for soft interactions: a spectroscopic benchmark data set for weak and strong hydrogen...

Area of Science:

• Computational Chemistry
• Spectroscopy
• Physical Chemistry

Background:

• Hydrogen-bonded complexes are crucial in various chemical and biological processes.
• Accurate theoretical prediction of their properties is essential for understanding these interactions.
• Existing benchmarks may not sufficiently cover the diversity of non-covalent interactions.

Purpose of the Study:

• To assemble and refine an experimental benchmark database for non-covalent interactions.
• To facilitate the evaluation of theoretical methods for predicting properties of hydrogen-bonded systems.
• To identify systematic errors and performance trends in density functional theory (DFT) calculations.

Main Methods:

• Compilation of experimental spectroscopic data (rotational constants, vibrational frequencies, energy differences).
• Development of the Experimental Non-Covalent Harmonic (ENCH-51) database with 51 entries.
• Back-correction of experimental observables to match theoretical calculations (equilibrium structures, harmonic frequencies, energies).
• Assessment of DFT methods (B3LYP-D3, PBE0-D3, M06-2X) using a quadruple-zeta basis set.

Main Results:

• The ENCH-51 database provides a rigorous benchmark for theoretical methods.
• Systematic errors, error compensation, and selective performance of DFT functionals were identified.
• The study highlights the importance of benchmarking methodologies for theoretical chemistry.
• Discrepancies between theory and experiment were analyzed for structural, vibrational, and energetic properties.

Conclusions:

• The ENCH-51 database serves as a valuable resource for validating computational chemistry methods.
• DFT methods show varying performance, emphasizing the need for careful method selection.
• Further expansion of the database across chemical space and theoretical methods is recommended.