title: Low energy isomers of (H2O)25 from a hierarchical method based on Monte Carlo temperature basin paving and molecular tailoring approaches benchmarked by MP2 calculations.
abstract: We report new global minimum candidate structures for the (H2O)25 cluster that are lower in energy than the ones reported previously and correspond to hydrogen bonded networks with 42 hydrogen bonds and an interior, fully coordinated water molecule. These were obtained as a result of a hierarchical approach based on initial Monte Carlo Temperature Basin Paving sampling of the cluster's Potential Energy Surface with the Effective Fragment Potential, subsequent geometry optimization using the Molecular Tailoring Approach with the fragments treated at the second order Møller-Plesset (MP2) perturbation (MTA-MP2) and final refinement of the entire cluster at the MP2 level of theory. The MTA-MP2 optimized cluster geometries, constructed from the fragments, were found to be within <0.5 kcal/mol from the minimum geometries obtained from the MP2 optimization of the entire (H2O)25 cluster. In addition, the grafting of the MTA-MP2 energies yields electronic energies that are within <0.3 kcal/mol from the MP2 energies of the entire cluster while preserving their energy rank order. Finally, the MTA-MP2 approach was found to reproduce the MP2 harmonic vibrational frequencies, constructed from the fragments, quite accurately when compared to the MP2 ones of the entire cluster in both the HOH bending and the OH stretching regions of the spectra.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India.
authors.forename: Nityananda
authors.initials: N
authors.lastname: Sahu
authors.affiliation: Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India.
authors.forename: Shridhar R
authors.initials: SR
authors.lastname: Gadre
authors.affiliation: School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
authors.forename: Avijit
authors.initials: A
authors.lastname: Rakshit
authors.affiliation: School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
authors.forename: Pradipta
authors.initials: P
authors.lastname: Bandyopadhyay
authors.affiliation: Physical Sciences Division, Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MS K1-83, Richland, Washington 99352, USA.
authors.forename: Evangelos
authors.initials: E
authors.lastname: Miliordos
authors.affiliation: Physical Sciences Division, Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MS K1-83, Richland, Washington 99352, USA.
authors.forename: Sotiris S
authors.initials: SS
authors.lastname: Xantheas
mesh_terms: D006860:Hydrogen Bonding; D007536:Isomerism; D008958:Models, Molecular; D008968:Molecular Conformation; D009010:Monte Carlo Method; D011789:Quantum Theory; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water