Choosing a density functional for modeling adsorptive hydrogen storage: reference quantum mechanical calculations and...

Area of Science:

• Computational chemistry
• Materials science
• Physical chemistry

Background:

• Hydrogen storage in carbon materials is crucial for energy applications.
• Density functional theory (DFT) is widely used but yields varied hydrogen binding energies.
• Accurate computational data is needed to validate DFT predictions.

Purpose of the Study:

• To provide high-level quantum mechanical (QM) reference data for hydrogen binding energies.
• To assess the accuracy of various DFT functionals against coupled-cluster (CCSD(T)) calculations.
• To guide the selection of appropriate DFT methods for hydrogen storage material design.

Main Methods:

• Coupled-cluster singles and doubles with perturbative triples (CCSD(T)) calculations.
• Complete basis set (CBS) limit estimation.
• Verification against diffusion quantum Monte Carlo (DMC) for one complex.
• Calculation of reference binding curves for model compounds.

Main Results:

• DFT-D3 accurately predicts weak hydrogen adsorption on coronene.
• Most dispersion-corrected DFT functionals overestimate weak interactions.
• Less empirical dispersion functionals better describe strong binding in polar complexes like coroB2Li22H2.
• Significant variation in DFT predictions for hydrogen binding energies.

Conclusions:

• CCSD(T) and CBS estimates provide reliable reference data for hydrogen binding.
• The study highlights the strengths and weaknesses of various DFT functionals.
• Results serve as a guide for selecting DFT methods for evaluating hydrogen storage materials.