We report a systematic study of the weak chemical bond between two benzene molecules. We first show that it is possible to obtain a very good description of the C_2 dimer and the benzene molecule, by using pseudopotentials for the chemically inert 1s electrons, and a resonating valence bond wave function as a variational ansatz, expanded on a relatively small Gaussian basis set. We employ an improved version of the stochastic reconfiguration technique to optimize the many-body wave function, which is the starting point for highly accurate simulations based on the lattice regularized diffusion Monte Carlo (LRDMC) method. This projection technique provides a rigorous variational upper bound for the total energy, even in the presence of pseudopotentials, and allows to improve systematically the accuracy of the trial wave function, which already yields a large fraction of the dynamical and non-dynamical electron correlation. We show that the energy dispersion of two benzene molecules in the parallel displaced geometry is significantly deeper than the face-to-face configuration. However, contrary to previous studies based on post Hartree-Fock methods, the binding energy remains weak (~ 2 kcal/mol) also in this geometry, and its value is in agreement with the most accurate and recent experimental findings.

Weak binding between two aromatic rings: Feeling the van der Waals attraction by quantum Monte Carlo methods / Sorella, Sandro; Michele, Casula; Dario, Rocca. - In: THE JOURNAL OF CHEMICAL PHYSICS. - ISSN 0021-9606. - 127:1(2007), pp. 1-12. [10.1063/1.2746035]

Weak binding between two aromatic rings: Feeling the van der Waals attraction by quantum Monte Carlo methods

Sorella, Sandro;
2007-01-01

Abstract

We report a systematic study of the weak chemical bond between two benzene molecules. We first show that it is possible to obtain a very good description of the C_2 dimer and the benzene molecule, by using pseudopotentials for the chemically inert 1s electrons, and a resonating valence bond wave function as a variational ansatz, expanded on a relatively small Gaussian basis set. We employ an improved version of the stochastic reconfiguration technique to optimize the many-body wave function, which is the starting point for highly accurate simulations based on the lattice regularized diffusion Monte Carlo (LRDMC) method. This projection technique provides a rigorous variational upper bound for the total energy, even in the presence of pseudopotentials, and allows to improve systematically the accuracy of the trial wave function, which already yields a large fraction of the dynamical and non-dynamical electron correlation. We show that the energy dispersion of two benzene molecules in the parallel displaced geometry is significantly deeper than the face-to-face configuration. However, contrary to previous studies based on post Hartree-Fock methods, the binding energy remains weak (~ 2 kcal/mol) also in this geometry, and its value is in agreement with the most accurate and recent experimental findings.
2007
127
1
1
12
014105
https://aip.scitation.org/doi/10.1063/1.2746035
Sorella, Sandro; Michele, Casula; Dario, Rocca
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11767/11561
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