Ionic liquids (ILs) have been researched widely as green design materials for a variety of applications, including carbon capture. Recently, research has investigated the properties of ionic liquids with multiple types of anions and cations; however, the mechanics of solvation in these more complex systems are not well understood. The spectral diffusion of asymmetric stretch frequency of CO2 has been found to be an excellent reporter of CO2 solvation structure and dynamics in ILs. A significant challenge is that simulations which can directly report this spectral diffusion are computationally expensive. Spectroscopic maps can empirically correlate observables from a molecular dynamics simulation to a frequency in a known structure and accurately estimate frequencies on fast timescales. We have developed efficient extraction algorithms to procure electric fields and Lennard-Jones potentials from molecular dynamics simulations. These variables have been used in previous spectroscopic maps for the CO2 asymmetric stretch frequency in ILs. Additionally, we have extracted new variables that were not directly available in the previous force field such as Pauli repulsion and dispersion forces, and tested their correlation to the vibrational frequency.

Extracting observables from molecular dynamics simulations of carbon dioxide in ionic liquids for spectroscopic mapping

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