152 research outputs found
The Thiocyanate Anion is a Primary Driver of Carbon Dioxide Capture by Ionic Liquids
Carbon dioxide, CO2, capture by room-temperature ionic liquids (RTILs) is a
vivid research area featuring both accomplishments and frustrations. This work
employs the PM7-MD method to simulate adsorption of CO2 by
1,3-dimethylimidazolium thiocyanate at 300 K. The obtained result evidences
that the thiocyanate anion plays a key role in gas capture, whereas the impact
of the 1,3-dimethylimidazolium cation is mediocre. Decomposition of the
computed wave function on the individual molecular orbitals confirms that
CO2-SCN binding extends beyond just expected electrostatic interactions in the
ion-molecular system and involves partial sharing of valence orbitals
Annealing Relaxation of Ultrasmall Gold Nanostructures
Except serving as an excellent gift on proper occasions, gold finds
applications in life sciences, particularly in diagnostics and therapeutics.
These applications were made possible by gold nanoparticles, which differ
drastically from macroscopic gold. Versatile surface chemistry of gold
nanoparticles allows coating with small molecules, polymers, biological
recognition molecules. Theoretical investigation of nanoscale gold is not
trivial, because of numerous metastable states in these systems. Unlike
elsewhere, this work obtains equilibrium structures using annealing simulations
within the recently introduced PM7-MD method. Geometries of the ultrasmall gold
nanostructures with chalcogen coverage are described at finite temperature, for
the first time
Competitive Solvation of the Imidazolium Cation by Water and Methanol
Imidazolium-based ionic liquids are widely used in conjunction with molecular
liquids for various applications. Solvation, miscibility and similar properties
are of fundamental importance for successful implementation of theoretical
schemes. This work reports competitive solvation of the 1,3-dimethylimidazolium
cation by water and methanol. Employing molecular dynamics simulations powered
by semiempirical Hamiltonian (electronic structure level of description), the
local structure nearly imidazolium cation is described in terms of radial
distribution functions. Although water and methanol are chemically similar,
water appears systematically more successful in solvating the
1,3-dimethylimidazolium cation. This result fosters construction of future
applications of the ternary ion-molecular systems
Competitive Solvation of (Bis)(trifluoromethanesulfonyl)imide Anion by Acetonitrile and Water
Competitive solvation of an ion by two or more solvents is one of the key
phenomena determining the identity of our world. Solvation in polar solvents
frequently originates from non-additive non-covalent interactions.
Pre-parametrized potentials poorly capture these interactions, unless the force
field derivation is repeated for every new system. Development cost increases
drastically as new chemical species are supplied. This work represents an
alternative simulation approach, PM7-MD, by coupling the latest semiempirical
parametrization, PM7, with equation-of-motion propagation scheme and
temperature coupling. Using a competitive solvation of
(bis)(trifluoromethanesulfonyl)imide anion in acetonitrile and water, the work
demonstrates efficiency and robustness of PM7-MD
Hydrogen Fluoride Capture by Imidazolium Acetate Ionic Liquid
Extraction of hydrofluoric acid (HF) from oils is a drastically important
problem in petroleum industry, since HF causes quick corrosion of pipe lines
and brings severe health problems to humanity. Some ionic liquids (ILs)
constitute promising scavenger agents thanks to strong binding to polar
compounds and tunability. PM7-MD simulations and hybrid density functional
theory are employed here to consider HF capture ability of ILs. Discussing the
effects and impacts of the cation and the anion separately and together, I will
evaluate performance of imidazolium acetate and outline systematic search
guidelines for efficient adsorption and extraction of HF
Nanoscale Carbon Greatly Enhances Mobility of a Highly Viscous Ionic Liquid
Ability to encapsulate molecules is one of the outstanding features of
nanotubes. The encapsulation alters physical and chemical properties of both
nanotubes and guest species. The latter normally form a separate phase,
exhibiting drastically different behavior compared to bulk. Ionic liquids (ILs)
and apolar carbon nanotubes (CNTs) are disparate objects; nevertheless, their
interaction leads to spontaneous CNT filling with ILs. Moreover, ionic
diffusion of highly viscous ILs can increase 5-fold inside CNTs, approaching
that of molecular liquids, even though the confined IL phase still contains
exclusively ions. We exemplify these unusual effects by computer simulation on
a highly hydrophilic, electrostatically structured, and immobile
1-ethyl-3-methylimidazolium chloride, [C2C1IM][Cl]. Self-diffusion constants
and energetic properties provide microscopic interpretation of the observed
phenomena. Governed by internal energy and entropy rather than external work,
the kinetics of CNT filling is characterized in detail. The significant growth
of the IL mobility induced by nanoscale carbon promises important advances in
electricity storage devices
- …