Department of Physics, Faculty of Science, The University of Ngaoundere, P.O. Box 454, Ngaoundere, Cameroon.
Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa.
J Chem Phys. 2018 Dec 28;149(24):244301. doi: 10.1063/1.5053172.
We investigated in this work the structures and relative population of large sized protonated ammonia clusters, , = 18, 20, 25, 30. To this end, we generated initial geometries using the ABCluster code. The 30 most stable geometries for each of the clusters have been fully optimized at the APFD/6-31++g(d,p) level of theory. The results show that the proton is asymmetrically shared by two ammonia molecules to form the complex. The complex occupies the center of the structures, and it is gradually solvated with increasing cluster size. For = 25 and = 30, the first solvation shell of is completely filled with some ammonia molecules present in the second solvation shell. Besides, we have reported the relative population of the investigated clusters at the thermodynamic equilibrium. As a result, the three most stable structures dominate the population of the clusters. For each cluster size, we found that the IR spectra of these three most stable structures are in agreement with experiments. This agreement could be an indication of the reliability of our investigations. Overall, the structures of large sized protonated ammonia clusters are cage-like and exhibit an amorphous behavior.
在这项工作中，我们研究了尺寸较大的质子化氨团簇、 = 18、20、25、30 的结构和相对丰度。为此，我们使用 ABCluster 代码生成初始结构。对每个团簇的 30 个最稳定结构，我们在 APFD/6-31++g(d,p)理论水平上进行了全优化。结果表明，质子被两个氨分子不对称地共享，形成 复合物。 复合物占据结构的中心，并随着团簇尺寸的增加逐渐被溶剂化。对于 = 25 和 = 30， 的第一个溶剂化壳层完全被存在于第二个溶剂化壳层中的一些氨分子填充。此外，我们还报告了在热力学平衡下研究的团簇的相对丰度。结果表明，三个最稳定的结构主导了团簇的丰度。对于每个团簇尺寸，我们发现这三个最稳定结构的红外光谱与实验结果一致。这种一致性可能表明我们的研究是可靠的。总的来说，大尺寸质子化氨团簇的结构呈笼状，并表现出无定形行为。
