A Structural and Dynamical Analysis of Ionic Liquids and Aqueous Hydroxide Solutions via Molecular Dynamics

In this dissertation, I have simulated many ionic liquid and aqueous solutions using classical and ab initio molecular dynamics simulations. First, I validated the use of an electric field time correlation function as a substitute for a frequency time correlation function. This substitute method of analysis avoids calculating a spectroscopic map for any new solution of interest, allowing significantly more spectral diffusion dynamics to be studied on a reasonable time scale with less computational expenditure. A series of nineteen alcohol molecule vibrational reporters were simulated in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)-imide to understand structural and dynamical effects of altering the size and shape of the vibrational reporters. Branched alcohols slowed ionic liquid dynamics more than any other class, while primary alcohols and aromatic alcohols displayed similar time scales when the alkyl chain lengths were identical.

The latter part of this manuscript studies dilute aqueous solutions with ab initio molecular dynamics simulations. While the presence of differing cations in aqueous hydroxide solutions does not largely affect the water solvation structure around hydroxide, the cations themselves interact quite differently with hydroxide. Namely, lithium delocalizes protons donating a hydrogen bond to hydroxide more strongly than sodium ions. Ongoing research includes calculating the free energy profile of ion-ion pairs using the weighted histogram analysis method.