Low-lying structures and stabilities of large water clusters: investigation based on the combination of the AMOEBA potential and generalized energy-based fragmentation approach.
Based on a large database of local minima obtained with the polarizable AMOEBA potential, the generalized energy-based fragmentation (GEBF) approach is applied to locate low-lying structures of water clusters (H(2)O)(n) in the range n = 20-30, at the B3LYP and MP2 levels. Our results show that the relative stabilities of isomers predicted by the AMOEBA empirical potential differ noticeably from those predicted by GEBF-B3LYP/6-311++G(d,p) and GEBF-MP2/6-311++G(3df,2p) calculations. From GEBF-B3LYP energies with zero-point vibrational energy corrections, one can see that for water clusters in the range n = 20-30 the transition from one-centered to two-centered cage structure occurs at n = 26. With increasing cluster size, the number of H-bonds per water molecule in the lowest-energy structures shows a gradually increasing trend, and the proportion of four-coordinated water molecules gradually increases, as expected for large water clusters. Based on GEBF-MP2/6-311++G(3df,2p) energies (instead of GEBF-B3LYP/6-311++G(d,p) energies), different lowest-energy structures can be found for six cluster sizes in the range n = 20-30, suggesting the significance of the dispersion interaction in determining the relative energies of low-lying water clusters.
Yang
Zhen
Z
School of Chemistry and Chemical Engineering, Key Laboratory of Mesoscopic Chemistry of the Ministry of Education, Institute of Theoretical and Computational Chemistry, Nanjing University, Nanjing 210093, People's Republic of China.
Hua
Shugui
S
Hua
Weijie
W
Li
Shuhua
S
D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
D014867:Water