title: Fragment Quantum Mechanical Method for Large-Sized Ion-Water Clusters.
abstract: Fragmentation methods have been widely studied for computing quantum mechanical (QM) energy of medium-sized water clusters, but less attention has been paid to large-sized ion-water clusters, in which many-body QM interaction is more significant, because of the charge-transfer effect between ions and water molecules. In this study, we utilized electrostatically embedded generalized molecular fractionation (EE-GMF) method for full QM calculation of the large-sized ion-water clusters (up to 15 Na+and 15 Cl-ions solvated with 119 water molecules). Through systematic validation using different fragment sizes, we show that, by using distance thresholds of 6 Å for both the two-body and three-body QM interactions, the EE-GMF method is capable of providing accurate ground-state energies of large-sized ion-water clusters at different ab initio levels (including HF, B3LYP, M06-2X, and MP2) with significantly reduced computational cost. The deviations of EE-GMF from full system calculations are within a few kcal/mol. The result clearly shows that the calculated energies of the ion-water clusters using EE-GMF are close to converge after the distance thresholds are larger than 6 Å for both the two-body and three-body QM interactions. This study underscores the importance of the three-body interactions in ion-water clusters. The EE-GMF method can also accurately reproduce the relative energy profiles of the ion-water clusters.
authors.affiliation: State Key Laboratory of Natural Medicines, Department of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University , Nanjing, 210009, China.
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Natural Medicines, Department of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University , Nanjing, 210009, China.
authors.forename: Lian-Wen
authors.initials: LW
authors.lastname: Qi
authors.affiliation: School of Chemistry and Molecular Engineering, East China Normal University , Shanghai, 200062, China.|NYU-ECNU Center for Computational Chemistry at NYU Shanghai , Shanghai, 200062, China.|Department of Chemistry, New York University , New York, New York 10003, United States.
authors.forename: John Z H
authors.identifier: http://orcid.org/0000-0003-4612-1863
authors.initials: JZH
authors.lastname: Zhang
authors.affiliation: School of Chemistry and Molecular Engineering, East China Normal University , Shanghai, 200062, China.|NYU-ECNU Center for Computational Chemistry at NYU Shanghai , Shanghai, 200062, China.
authors.forename: Xiao
authors.identifier: http://orcid.org/0000-0002-4199-8175
authors.initials: X
authors.lastname: He