Anion effects in the scattering of CO2 from the room-temperature ionic liquids [bmim][BF4] and [bmim][Tf2N]: Insights from quantum mechanics/molecular mechanics trajectories

Xiaohu Li, George C Schatz, David J. Nesbitt

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19 Citations (Scopus)

Abstract

Quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations have been carried out to model the scattering of hyperthermal (15 kcal/mol) CO2 on the surfaces of two common imidazolium based room-temperature ionic liquids (RTILs) [bmim][BF4] and [bmim][Tf2N]. Good agreement was achieved in comparison with experiment. The [bmim][BF4] surface is found to be more absorptive of CO2 than [bmim][Tf2N], which leads to greater loss in translational energy and less rotational excitation of CO 2's that scatter from [bmim][BF4]. These differences are found to result from a interplay of differences in the structure of the interface and the strength of interactions that depend on anion identity. Our results also suggest that CO2 interacts strongly with ionic species on the RTIL surfaces due to the large induced dipole moments on CO2 during the collisions. The inclusion of electronic polarization is critical in determining the final rotational excitation of CO2 compared to results from an MM model with fixed charge.

Original languageEnglish
Pages (from-to)3587-3602
Number of pages16
JournalJournal of Physical Chemistry B
Volume116
Issue number11
DOIs
Publication statusPublished - Mar 22 2012

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Ionic Liquids
Molecular mechanics
Quantum theory
Ionic liquids
Anions
quantum mechanics
Negative ions
Trajectories
trajectories
Scattering
anions
liquid surfaces
room temperature
liquids
scattering
excitation
dipole moments
Dipole moment
inclusions
Carbon Monoxide

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Materials Chemistry
  • Surfaces, Coatings and Films

Cite this

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title = "Anion effects in the scattering of CO2 from the room-temperature ionic liquids [bmim][BF4] and [bmim][Tf2N]: Insights from quantum mechanics/molecular mechanics trajectories",
abstract = "Quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations have been carried out to model the scattering of hyperthermal (15 kcal/mol) CO2 on the surfaces of two common imidazolium based room-temperature ionic liquids (RTILs) [bmim][BF4] and [bmim][Tf2N]. Good agreement was achieved in comparison with experiment. The [bmim][BF4] surface is found to be more absorptive of CO2 than [bmim][Tf2N], which leads to greater loss in translational energy and less rotational excitation of CO 2's that scatter from [bmim][BF4]. These differences are found to result from a interplay of differences in the structure of the interface and the strength of interactions that depend on anion identity. Our results also suggest that CO2 interacts strongly with ionic species on the RTIL surfaces due to the large induced dipole moments on CO2 during the collisions. The inclusion of electronic polarization is critical in determining the final rotational excitation of CO2 compared to results from an MM model with fixed charge.",
author = "Xiaohu Li and Schatz, {George C} and Nesbitt, {David J.}",
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T2 - Insights from quantum mechanics/molecular mechanics trajectories

AU - Li, Xiaohu

AU - Schatz, George C

AU - Nesbitt, David J.

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N2 - Quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations have been carried out to model the scattering of hyperthermal (15 kcal/mol) CO2 on the surfaces of two common imidazolium based room-temperature ionic liquids (RTILs) [bmim][BF4] and [bmim][Tf2N]. Good agreement was achieved in comparison with experiment. The [bmim][BF4] surface is found to be more absorptive of CO2 than [bmim][Tf2N], which leads to greater loss in translational energy and less rotational excitation of CO 2's that scatter from [bmim][BF4]. These differences are found to result from a interplay of differences in the structure of the interface and the strength of interactions that depend on anion identity. Our results also suggest that CO2 interacts strongly with ionic species on the RTIL surfaces due to the large induced dipole moments on CO2 during the collisions. The inclusion of electronic polarization is critical in determining the final rotational excitation of CO2 compared to results from an MM model with fixed charge.

AB - Quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations have been carried out to model the scattering of hyperthermal (15 kcal/mol) CO2 on the surfaces of two common imidazolium based room-temperature ionic liquids (RTILs) [bmim][BF4] and [bmim][Tf2N]. Good agreement was achieved in comparison with experiment. The [bmim][BF4] surface is found to be more absorptive of CO2 than [bmim][Tf2N], which leads to greater loss in translational energy and less rotational excitation of CO 2's that scatter from [bmim][BF4]. These differences are found to result from a interplay of differences in the structure of the interface and the strength of interactions that depend on anion identity. Our results also suggest that CO2 interacts strongly with ionic species on the RTIL surfaces due to the large induced dipole moments on CO2 during the collisions. The inclusion of electronic polarization is critical in determining the final rotational excitation of CO2 compared to results from an MM model with fixed charge.

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