Abstract
We present a comprehensive benchmark study of the adsorption energy of a single water molecule on the (001) LiH surface using periodic coupled cluster and quantum Monte Carlo theories. We benchmark and compare different implementations of quantum chemical wave function based theories in order to verify the reliability of the predicted adsorption energies and the employed approximations. Furthermore we compare the predicted adsorption energies to those obtained employing widely used van der Waals density-functionals. Our findings show that quantum chemical approaches are becoming a robust and reliable tool for condensed phase electronic structure calculations, providing an additional tool that can also help in potentially improving currently available van der Waals density-functionals.
Highlights
In this work, we consider an ab initio description of the true many-body wave function for a molecular adsorption problem
In order to assess the accuracy of different theories and computational procedures, we study the adsorption of a single water molecule on the (001) surface of lithium hydride (LiH)
We present the results of DFT calculations, different periodic MP2 and coupled-cluster techniques, and compare these methods with Diffusion Monte Carlo (DMC)
Summary
We consider an ab initio description of the true many-body wave function for a molecular adsorption problem. Two contrasting yet complementary approaches which we consider here are those from the field of quantum chemical Fock-space expansions of the wave function and a stochastic representation from the Diffusion Monte Carlo (DMC) technique.. Two contrasting yet complementary approaches which we consider here are those from the field of quantum chemical Fock-space expansions of the wave function and a stochastic representation from the Diffusion Monte Carlo (DMC) technique.10 These wave function based approaches offer a thorough description of quantum many-body effects through a direct treatment of electronic correlation. DMC is a real-space quantum Monte Carlo (QMC) method, where the real-space configurations of all N-electrons are sampled stochastically This stochastic distribution of electrons is evolved toward a sampling of the ground-state distribution of electrons via an imaginary-time propagator, which exponentially filters out the higher-lying eigenfunctions of the Hamiltonian from the distribution. This sampling would be exact if it were not for the “Fermion sign problem,” where the sampling collapses to the lower-energy symmetric
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