Locality in amino-acid based imidazolium ionic liquids

Area of Science:

• Computational chemistry
• Materials science
• Physical chemistry

Background:

• Ionic liquids (ILs) are tunable solvents with diverse applications.
• Understanding their polarization is crucial for predicting their behavior.
• Amino-acid based ILs offer unique properties but require detailed investigation.

Purpose of the Study:

• To investigate the polarization of amino-acid based imidazolium ionic liquids using ab initio molecular dynamics.
• To evaluate various charge schemes for accurately predicting dipole moments.
• To analyze electrostatic interactions and vibrational spectra for a deeper understanding of IL behavior.

Main Methods:

• Ab initio molecular dynamics (AIMD) simulations with full polarization.
• Analysis of electric dipole moment distribution and polarization.
• Comparison of Wannier, Blöchl, Löwdin, Mulliken, and Voronoi tessellation charge schemes.
• Calculation of angular probability distribution for electrostatic interactions.
• Analysis of IR and Raman spectra.

Main Results:

• AIMD with full polarization provides insights into IL polarization.
• The choice of charge scheme significantly impacts dipole moment prediction.
• Anion and cation contributions to polarizability are distinct.
• Electrostatic interactions showed no preferential alignment above 700 pm.
• IR and Raman spectra of [C2C1Im][ala] showed experimental consistency and differentiated anion/cation components.

Conclusions:

• Accurate prediction of IL polarization requires careful selection of charge schemes.
• Understanding individual anion and cation contributions is vital.
• AIMD is a powerful tool for characterizing complex IL systems.
• The study provides a foundation for designing ILs with specific properties.