Performance of dispersion-corrected density functional theory for the interactions in ionic liquids
Stefan Grimme1, Waldemar Hujo, Barbara Kirchner
1Mulliken Center for Theoretical Chemistry, Institut für Physikalsche und Theoretische Chemie, Universität Bonn, Beringstr. 4, D-53115 Bonn, Germany. grimme@thch.uni-bonn.de
Physical Chemistry Chemical Physics : PCCP
|March 2, 2012
Summary
Dispersion corrections significantly stabilize ionic liquid building blocks, shortening distances and increasing vibrational frequencies. Dispersion-corrected hybrid functionals accurately model these interactions, outperforming semi-local methods.
Area of Science:
- Computational Chemistry
- Materials Science
Background:
- Ionic liquids are crucial building blocks in various chemical applications.
- Accurate modeling of cation-anion interactions is essential for understanding ionic liquid properties.
Purpose of the Study:
- To compute potential energy curves for ionic liquid building units.
- To evaluate the performance of dispersion-corrected density functional theory (DFT) methods.
- To compare DFT results with high-level theoretical calculations.
Main Methods:
- Dispersion-corrected DFT methods, including non-local van der Waals (DFT-NL) and DFT-D3.
- Calculations performed on cation-anion associates of imidazolium and phosphonium cations with chloride, dicyanamide, and acetate anions.
- Reference data obtained using MP2/CBS and CCSD(T)/CBS extrapolation methods.
Main Results:
- Dispersion energy provides substantial stabilization (5-7 kcal mol(-1)).
- Equilibrium distances are reduced, and vibrational frequencies increase with dispersion corrections.
- Dispersion-corrected hybrid functionals show excellent agreement with CCSD(T) reference data (1-2% deviation).
Conclusions:
- Dispersion corrections are vital for accurate modeling of ionic liquid interactions.
- DFT-D3 method performs well, likely due to error cancellation.
- Dispersion-corrected hybrid functionals are recommended over semi-local DFT for these systems.
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