Dynamic QM/MM: A Hybrid Approach to Simulating Gas–Liquid Interactions - Multiscale Molecular Methods in Applied Chemistry - page 59

In both of these liquids the computed surface topology demonstrated that the large
anion and the ethyl-chain are equally present at the surface, while the longer C 12 -
chain extends well out of the surface, thus exposing a significant amount of
accessible H to the incoming O atoms.
Upon collision with Ar, some translational energy is transferred into the [emim]
[NO 3 ] surface causing minor changes in the local chemistry as shown in Table 1 .
Nearly all of the incident Ar atoms scatter from the surface (a probability of 0.91)
with a small fraction trapped at the end of the simulation time of 7.3 ps. The
momentum transfer causes on average two to three proton transfers to occur
between the imidazolium ring and the anion (see Table 2 ), thus neutralizing the

Table 1 Probabilities for
scattering Ar and O( 3 P) from
an [emim][NO 3 ] surface,
including the distribution of
each nascent product

From O( 3 P)

From Ar

Total a 0.17 0.01 0.57 0.02

Incident atom b 0.91 0.03 0.23 0.01

HNO 3 0.06 0.01 0.04 0.006

emim c 0.10 0.01 0.12 0.01

emim + [NO 3 ] d 0.01 0.003 0.05 0.006

O - 0.13 0.01

OH - 0.04 0.005

O 2 - 0.02 0.005

HNO 2 - 0.05 0.007

Me/Et fragment e - 0.02 0.005

IM-chain f - 0.01 0.003

IM-chain fragment g - 0.04 0.006
a For Ar this value includes the sum of all non-Ar products; for O,
this includes all desorption products
b Includes only desorption products containing the incident atom
c Refers to the neutral species from the cation [emim] after
loss of H þ
d Refers to any pairs or groups derived from the imidazolium ring
(cation or neutral) with the anion
e Methyl or ethyl fragment from elimination of hydrocarbon
from ring
f

The unfolded imidazolium ring from ring scission - O addition
g

A piece of the unfolded ring from ring fragmentation - O
addition

Table 2 Distribution of
number of proton transfers
and cation/anion pair
recombinations

Proton transfer Incident O Incident Ar

0 0.12 0.01 0.13 0.01

1 0.29 0.02 0.21 0.01

2 0.35 0.02 0.31 0.02

3 0.20 0.01 0.30 0.02

4 0.04 0.01 0.05 0.01

5 0.00 0.00

[emim] þ [NO 3 ] !

emim-ONO 2 a 0.12 0.01 0.12 0.01

a

An oxygen from NO 3 attaches to the imidazolium ring