1 research outputs found
Atomistic Insight into Orthoborate-Based Ionic Liquids: Force Field Development and Evaluation
We have developed an all-atomistic
force field for a new class
of halogen-free chelated orthoborate-phosphonium ionic liquids. The
force field is based on an AMBER framework with determination of force
field parameters for phosphorus and boron atoms, as well as refinement
of several available parameters. The bond and angle force constants
were adjusted to fit vibration frequency data derived from both experimental
measurements and <i>ab initio</i> calculations. The force
field parameters for several dihedral angles were obtained by fitting
torsion energy profiles deduced from <i>ab initio</i> calculations.
To validate the proposed force field parameters, atomistic simulations
were performed for 12 ionic liquids consisting of tetraalkylphosphonium
cations and chelated orthoborate anions. The predicted densities for
neat ionic liquids and the [P<sub>6,6,6,14</sub>]Â[BOB] sample, with
a water content of approximately 2.3–2.5 wt %, are in excellent
agreement with available experimental data. The potential energy components
of 12 ionic liquids were discussed in detail. The radial distribution
functions and spatial distribution functions were analyzed and visualized
to probe the microscopic ionic structures of these ionic liquids.
There are mainly four high-probability regions of chelated orthoborate
anions distributed around tetraalkylphosphonium cations in the first
solvation shell, and such probability distribution functions are strongly
influenced by the size of anions