Polarizability in ionic liquid simulations causes hidden breakdown of linear response theory
Esther Heid1, Christian Schröder
1University of Vienna, Faculty of Chemistry, Department of Computational Biological Chemistry, Währingerstraße 19, A-1090 Vienna, Austria. christian.schroeder@univie.ac.at.
Physical Chemistry Chemical Physics : PCCP
|January 3, 2019
Summary
Linear response theory (LRT) has limitations in simulating solvation dynamics for ionic liquids. Induced contributions in polarizable simulations fail to obey LRT, unlike permanent dipoles.
Area of Science:
- Computational chemistry
- Physical chemistry
- Materials science
Background:
- Linear response theory (LRT) is widely used in computer simulations for solvation dynamics.
- Its computational efficiency makes it attractive for large systems like ionic liquids.
- The validity of LRT for complex systems, especially ionic liquids, remains a subject of debate.
Purpose of the Study:
- To investigate the validity of linear response theory (LRT) in computer simulations of solvation dynamics.
- To analyze the contributions of permanent dipoles and induced dipoles to the solvation response in ionic liquids.
- To determine the applicability of LRT for cation and anion dynamics in ionic liquids.
Main Methods:
- Large-scale computer simulations were employed.
- The study focused on solvation dynamics, specifically the time-dependent Stokes shift.
- Simulations considered both permanent dipoles and induced contributions in polarizable models.
Main Results:
- The contribution of permanent dipoles to the solvation response partially adheres to LRT.
- Induced contributions from polarizable simulations demonstrate a failure of LRT.
- LRT's validity is compromised for individual ion contributions (cation and anion) in ionic liquids.
Conclusions:
- Linear response theory (LRT) shows limitations when applied to the induced contributions in polarizable simulations of ionic liquids.
- While permanent dipoles show some adherence to LRT, induced effects lead to its failure for ion-specific dynamics.
- These findings highlight the need for caution when using LRT for detailed solvation dynamics in complex systems like ionic liquids.
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