Dispersion interactions in room-temperature ionic liquids: results from a non-empirical density functional
Jorge Kohanoff1, Carlos Pinilla, Tristan G A Youngs
1Atomistic Simulation Centre, Queen's University Belfast, Belfast BT7 1NN, Northern IrelandSchool of Chemistry, University of Bristol, Bristol BS2 1TS, United Kingdom. j.kohanoff@qub.ac.uk
The Journal of Chemical Physics
|October 28, 2011
Summary
This study enhances understanding of van de Waals interactions in ionic liquids using advanced density functional theory. Results show improved structural predictions for crystalline phases, outperforming previous methods.
Area of Science:
- Computational Chemistry
- Materials Science
- Condensed Matter Physics
Background:
- Ionic liquids, particularly imidazolium-based ones, are crucial in various chemical applications.
- Accurate modeling of van der Waals (VDW) interactions is essential for predicting their properties.
- Traditional density functional theory (DFT) approximations (LDA, GGA) often struggle with VDW forces.
Purpose of the Study:
- To investigate the role of VDW interactions in imidazolium-based room-temperature ionic liquids.
- To evaluate a new non-empirical functional for DFT calculations of ionic liquids.
- To improve the accuracy of structural and energetic predictions for ionic liquid crystals and clusters.
Main Methods:
- Density Functional Theory (DFT) calculations.
- Utilizing a recently developed non-empirical functional implemented in the SIESTA code.
- Analysis of crystalline phases, equilibrium structure, and lattice parameters.
- Investigation of neutral and charged clusters for specific ionic liquids ([bmim][Tf], [mmim][Cl]).
Main Results:
- The non-empirical functional significantly improves equilibrium distances and volumes compared to LDA and GGA.
- Intramolecular geometries are accurately retained, while intermolecular interactions are better described.
- An optimized version of the functional yields results within 2% of experimental data for solids.
- The study provides insights into the polymorphism of [bmim][Cl] crystals.
Conclusions:
- The employed non-empirical functional offers superior accuracy for modeling VDW interactions in ionic liquids.
- This approach validates the use of empirical force fields for cluster studies.
- The findings pave the way for more reliable computational studies of ionic liquid behavior.
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