Water 26-mers Drawn from Bulk Simulations: Benchmark Binding Energies for Unprecedentedly Large Water Clusters and Assessment of the Electrostatically Embedded Three-Body and Pairwise Additive Approximations.
It is important to test methods for simulating water, but small water clusters for which benchmarks are available are not very representative of the bulk. Here we present benchmark calculations, in particular CCSD(T) calculations at the complete basis set limit, for water 26-mers drawn from Monte Carlo simulations of bulk water. These clusters are large enough that each water molecule participates in 2.5 hydrogen bonds on average. The electrostatically embedded three-body approximation with CCSD(T) embedded dimers and trimers reproduces the relative binding energies of eight clusters with a mean unsigned error (MUE, kcal per mole of water molecules) of only 0.009 and 0.015 kcal for relative and absolute binding energies, respectively. Using only embedded dimers (electrostatically embedded pairwise approximation) raises these MUEs to 0.038 and 0.070 kcal, and computing the energies with the M11 exchange-correlation functional, which is very economical, yields errors of only 0.029 and 0.042 kcal.
Institute for Chemistry, Chemnitz University of Technology, Straße der Nationen 62, 09111 Chemnitz, Germany.|Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
Joachim
J
Friedrich
Institute for Chemistry, Chemnitz University of Technology, Straße der Nationen 62, 09111 Chemnitz, Germany.|Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
Haoyu
H
Yu
Institute for Chemistry, Chemnitz University of Technology, Straße der Nationen 62, 09111 Chemnitz, Germany.|Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
Hannah R
HR
Leverentz
Institute for Chemistry, Chemnitz University of Technology, Straße der Nationen 62, 09111 Chemnitz, Germany.|Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
Peng
P
Bai
Institute for Chemistry, Chemnitz University of Technology, Straße der Nationen 62, 09111 Chemnitz, Germany.|Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
J Ilja
JI
Siepmann
Institute for Chemistry, Chemnitz University of Technology, Straße der Nationen 62, 09111 Chemnitz, Germany.|Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
Donald G
DG
Truhlar
CCSD(T); correlation energy; density functional theory; explicitly correlated; fragment-based electronic structure methods; many-body expansion; overlapping fragments