Surface science using coupled cluster theory via local Wannier functions and in-RPA-embedding: the case of water on graphitic carbon nitride

TL;DR

This study combines local Wannier functions and in-RPA embedding with high-level coupled cluster theory to accurately compute water adsorption energies on graphitic carbon nitride, demonstrating rapid convergence and benchmarking against DFT.

Contribution

It introduces a novel embedding approach using localized Wannier orbitals with coupled cluster and RPA to efficiently study large surface-adsorbate systems.

Findings

High-level CCSD(T) calculations are feasible for large systems using the embedding approach.

Embedding CCSD(T) into RPA improves convergence of adsorption energies.

Benchmark results show differences between high-level methods and density functional calculations.

Abstract

A first-principles study of the adsorption of a single water molecule on a layer of graphitic carbon nitride employing an embedding approach is presented. The embedding approach involves an algorithm to obtain localized Wannier orbitals of various types expanded in a plane-wave basis and intrinsic atomic orbital projectors. The localized occupied orbitals are employed in combination with unoccupied natural orbitals to perform many-electron perturbation theory calculations of local fragments. The fragments are comprised of a set of localized orbitals close to the adsorbed water molecule. Although the surface model contains more than 100 atoms in the simulation cell, the employed fragments are small enough to allow for calculations using high-level theories up to the coupled cluster ansatz with single, double and perturbative triple particle-hole excitation operators (CCSD(T)). To correct for the missing long-range correlation energy contributions to the adsorption energy, we embed CCSD(T) theory into the direct random phase approximation, yielding rapidly convergent adsorption energies with respect to the fragment size. Convergence of computed binding energies with respect to the virtual orbital basis set is achieved employing a number of recently developed techniques. Moreover, we discuss fragment size convergence for a range of approximate many-electron perturbation theories. The obtained benchmark results are compared to a number of density functional calculations.