Structures, Energetics and Harmonic Vibrational Frequencies of Hydrated Halide Ions by the 2-body:Many-body Method
Thomas More Sexton, Caroline Anne Rader and Gregory S. Tschumper
Department of Chemistry and Biochemistry,
University of Mississippi, University, MS 38677-1848
Email: tmsexton@olemiss.edu, tschumpr@olemiss.edu
Energetics, optimized geometries, and harmonic vibrational frequencies of water-halide clusters (H2O)n X– (where n = 2 – 4 and X = F, Cl, Br, or I) are investigated with CCSD(T), MP2, and the QM:QM 2-body:Many-body CCSD(T):MP2 method [1-3], in which all one- and two-body terms are captured at the CCSD(T) level and three-body and higher terms are captured at the MP2 level. We have recently demonstrated that CCSD(T):MP2 (and even the analogous CCSD(T):RHF scheme) provides results of CCSD(T) quality at substantially reduced cost, while MP2 struggles to reproduce CCSD(T) frequencies for both water clusters and halide-water clusters [3,4]. Here the efficiency and accuracy of the 2b:Mb method is exploited to probe a more structurally diverse set of cluster configurations and to extend this analysis to larger tripleand quadruple-zeta quality correlation consistent basis sets to obtain CCSD(T) quality benchmark values for these halide-water complexes.
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DOI: 10.1002/jcc.10319
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[4]T. M. Sexton, G. S. Tschumper, Mol. Phys. accepted (2018).
DOI: 10.1080/00268976.2018.1554827