10.1021/jp512323k.s001
Shi-Tu Pei
Shi-Tu
Pei
Shuai Jiang
Shuai
Jiang
Yi-Rong Liu
Yi-Rong
Liu
Teng Huang
Teng
Huang
Kang-Ming Xu
Kang-Ming
Xu
Hui Wen
Hui
Wen
Yu-Peng Zhu
Yu-Peng
Zhu
Wei Huang
Wei
Huang
Properties
of Ammonium Ion–Water Clusters:
Analyses of Structure Evolution, Noncovalent Interactions, and Temperature
and Humidity Effects
American Chemical Society
2015
PW 91PW 3 pd
noncovalent interactions
binding energy
High humidity
Noncovalent Interactions
water molecules
ammonium ions
energy surfaces
growth route
PES
cluster growth
Structure Evolution
NH
cluster size increases
size clusters
alkali metal ion
2015-03-26 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Properties_of_Ammonium_Ion_Water_Clusters_Analyses_of_Structure_Evolution_Noncovalent_Interactions_and_Temperature_and_Humidity_Effects/2182438
Although ammonium ion–water
clusters are abundant in the
biosphere, some information regarding these clusters, such as their
growth route, the influence of temperature and humidity, and the concentrations
of various hydrated clusters, is lacking. In this study, theoretical
calculations are performed on ammonium ion–water clusters.
These theoretical calculations are focused on determining the following
characteristics: (1) the pattern of cluster growth; (2) the percentages
of clusters of the same size at different temperatures and humidities;
(3) the distributions of different isomers for the same size clusters
at different temperatures; (4) the relative strengths of the noncovalent
interactions for clusters of different sizes. The results suggest
that the dipole moment may be very significant for the ammonium ion–water
system, and some new stable isomers were found. The nucleation of
ammonium ions and water molecules is favorable at low temperatures;
thus, the clusters observed at high altitudes might not be present
at low altitudes. High humidity can contribute to the formation of
large ammonium ion–water clusters, whereas the formation of
small clusters may be favorable under low-humidity conditions. The
potential energy surfaces (PES) of these different sized clusters
are complicated and differ according to the distribution of isomers
at different temperatures. Some similar structures are observed between
NH<sub>4</sub><sup>+</sup>(H<sub>2</sub>O)<sub><i>n</i></sub> and M(H<sub>2</sub>O)<sub><i>n</i></sub> (where M represents
an alkali metal ion or water molecule); when <i>n</i> =
8, the clusters begin to form the closed-cage geometry. As the cluster
size increases, these interactions become progressively weaker. The
successive binding energy at the DF-MP2-F12/VDZ-F12 level is better
than that at the PW91PW91/6-311++G(3df, 3pd) level and is consistent
with the experimentally determined values.