First-Principles Study of Molecular Clusters Formed by Nitric Acid and Ammonia
First-Principles Study of Molecular Clusters Formed by Nitric Acid and Ammonia
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硝酸和氨形成分子簇的第一性原理研究
DOI：
10.1021/acs.jpca.6b09185
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发表时间：
2017
影响因子：
2.9
通讯作者：
Yang Jinlong
中科院分区：
文献类型：
--
作者：
Ling Jinfei;Ding Xunlei;Li Zhenyu;Yang Jinlong
用密度泛函理论研究了硝酸分子和氨分子形成的分子簇。对于 m,n≤ 4 的较小簇，考虑所有可能的 mdn 组合，而对于 5 ≤m,n≤ 8 范围内的较大簇，我们只考虑 |m–n| 的可能性。 ≤ 1。氢键网络的形成是这些团簇中重要的稳定机制。同时，除了最小的团簇之外，通常优选质子转移。这些簇的硝酸和氨蒸发速率是在明确考虑碰撞激活势垒和反应热力学的情况下计算的。然而，与硫酸和氨簇生长的情况不同，活化势垒在这里不起重要作用。如果条件不同，丰富物种的蒸发始终是首选。对于m=n>2的簇，氨蒸发比硝酸快。所有簇的稳定性可以通过优选物种的蒸发速率来定量评估。较大的簇通常更稳定。然而，结构基序转变点可能会出现例外情况。偏离化学计量 m=n 会显着降低团簇稳定性。对于由相同数量的分子形成的簇对来说，硝酸含量丰富的簇对更稳定，这决定了这些簇的生长途径。
Molecular clusters formed bymnitric acid molecules andnammonia molecules are studied with density functional theory. For smaller clusters withm,n≤ 4, all possible combinations ofmandnare considered, while for larger clusters in the 5 ≤m,n≤ 8 range we only consider the possibilities with |m–n| ≤ 1. Hydrogen bond network formation is an important stabilization mechanism in these clusters. At the same time, proton transfer is generally preferred except in the smallest clusters. Nitric acid and ammonia evaporation rates of these clusters are calculated with both collision activation barriers and reaction thermodynamics explicitly considered. However, unlike in the case of cluster growth from sulfuric acid and ammonia, activation barriers do not play an important role here. Ifmandnare unequal, evaporation of the abundant species is always preferred. For clusters withm=n> 2, ammonia evaporation is faster than nitric acid. Stabilities of all clusters can be quantitatively evaluated by the evaporation rate of the preferred species. Larger clusters are generally more stable. However, exceptions can occur at structure motif transition point. Deviation from the stoichiometry ofm=nsignificantly lowers the cluster stability. For a cluster pair formed by the same number of molecules, the nitric acid abundant one is more stable, which determines the growth pathway of these clusters.