Dynamics of Ionic Liquid through Intrinsic Vibrational Probes Using the Dispersion-Corrected DFT Functionals.

Area of Science:

• Computational Chemistry
• Materials Science
• Physical Chemistry

Background:

• Protic ionic liquids (PILs) like methylammonium formate (MAF) are crucial in various chemical applications.
• Understanding their spectral properties and hydrogen bonding dynamics is key to optimizing their performance.
• First principles molecular dynamics (MD) offers a powerful approach to probe these molecular-level behaviors.

Purpose of the Study:

• To investigate the spectral properties of methylammonium formate (MAF) using first principles MD simulations.
• To evaluate the impact of different density functional theory (DFT) exchange-correlation functionals on the calculated properties.
• To correlate simulation results with experimental observations for validation.

Main Methods:

• Density functional theory (DFT) based first principles molecular dynamics simulations.
• Application of various exchange-correlation functionals, including BLYP, PBE, and van der Waals (vdW)-corrected methods.
• Analysis of vibrational frequency distributions, time-frequency correlations, hydrogen-bond lifetimes, and orientation dynamics.

Main Results:

• Gradient approximation functionals (e.g., PBE, BLYP) indicate stronger hydrogen bonding in MAF compared to vdW-corrected methods.
• PBE functionals show minimal deviation in COO stretching frequencies from experimental data.
• Spectral diffusion dynamics reveal short, intermediate, and long time scales related to hydrogen bond rearrangements.
• DCACP correction to BLYP slows down dynamics and lengthens system response times.

Conclusions:

• The choice of DFT functional significantly influences the description of hydrogen bonding and spectral properties in MAF.
• PBE functionals provide a more accurate representation of COO stretching frequencies compared to other tested methods.
• MD simulations successfully capture the complex hydrogen bond dynamics and spectral diffusion in MAF, correlating with structural interactions.