TY - JOUR

T1 - Electrostatically embedded many-body correlation energy, with applications to the calculation of accurate second-order Møller-Plesset perturbation theory energies for large water clusters

AU - Dahlke, Erin E.

AU - Truhlar, Donald G.

PY - 2007/7

Y1 - 2007/7

N2 - The electrostatically embedded many-body expansion (EE-MB), previously applied to the total electronic energy, is here applied only to the electronic correlation energy (CE), combined with a Hartree-Fock calculation on the entire system. The separate treatment of the Hartree-Fock and correlation energies provides an efficient way to approximate correlation energy for extended systems. We illustrate this here by calculating accurate Møller-Plesset second-order perturbation theory (MP2) energies for a series of clusters ranging in size from 5 to 20 water molecules. In this new method, called EE-MB-CE, where MB is pairwise additive (PA) or three-body (3B), the full Hartree-Fock energy of a system of N monomers is calculated (i.e., the many-body expansion is carried out to the Nth order), while the EE-MB method is used to calculate the correlation energy of the system. We find that not only does this new method lead to better energetics than the original EE-MB method but also that one is able to obtain excellent agreement with full MP2 calculations by considering only a two-body expansion of the correlation energy, leading to a considerable savings in computational time as compared to the three-body expansion. Additionally, we propose the use of a cutoff to further reduce the number of two-body terms that must be calculated, and we show that if a cutoff of 6 Å is used, then one can eliminate up to 44% of the pairs and still calculate energies to within 0.1% of the net interaction energy of the full cluster.

AB - The electrostatically embedded many-body expansion (EE-MB), previously applied to the total electronic energy, is here applied only to the electronic correlation energy (CE), combined with a Hartree-Fock calculation on the entire system. The separate treatment of the Hartree-Fock and correlation energies provides an efficient way to approximate correlation energy for extended systems. We illustrate this here by calculating accurate Møller-Plesset second-order perturbation theory (MP2) energies for a series of clusters ranging in size from 5 to 20 water molecules. In this new method, called EE-MB-CE, where MB is pairwise additive (PA) or three-body (3B), the full Hartree-Fock energy of a system of N monomers is calculated (i.e., the many-body expansion is carried out to the Nth order), while the EE-MB method is used to calculate the correlation energy of the system. We find that not only does this new method lead to better energetics than the original EE-MB method but also that one is able to obtain excellent agreement with full MP2 calculations by considering only a two-body expansion of the correlation energy, leading to a considerable savings in computational time as compared to the three-body expansion. Additionally, we propose the use of a cutoff to further reduce the number of two-body terms that must be calculated, and we show that if a cutoff of 6 Å is used, then one can eliminate up to 44% of the pairs and still calculate energies to within 0.1% of the net interaction energy of the full cluster.

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U2 - 10.1021/ct700057x

DO - 10.1021/ct700057x

M3 - Article

AN - SCOPUS:36049038878

VL - 3

SP - 1342

EP - 1348

JO - Journal of Chemical Theory and Computation

JF - Journal of Chemical Theory and Computation

SN - 1549-9618

IS - 4

ER -