Abstract
The random phase approximation to the correlation energy often yields highly accurate results for condensed matter systems. However, ways how to improve its accuracy are being sought and here we explore the relevance of singles contributions for prototypical solid state systems. We set out with a derivation of the random phase approximation using the adiabatic connection and fluctuation dissipation theorem, but contrary to the most commonly used derivation, the density is allowed to vary along the coupling constant integral. This yields results closely paralleling standard perturbation theory. We re-derive the standard singles of Görling-Levy perturbation theory [A. Görling and M. Levy, Phys. Rev. A 50, 196 (1994)], highlight the analogy of our expression to the renormalized singles introduced by Ren and coworkers [Phys. Rev. Lett. 106, 153003 (2011)], and introduce a new approximation for the singles using the density matrix in the random phase approximation. We discuss the physical relevance and importance of singles alongside illustrative examples of simple weakly bonded systems, including rare gas solids (Ne, Ar, Xe), ice, adsorption of water on NaCl, and solid benzene. The effect of singles on covalently and metallically bonded systems is also discussed.
Highlights
In the last decade the interest in many body perturbation theory has risen significantly
The standard random phase approximation (RPA) performs reasonably well for rare gas solids,24 one observes that the binding energy is quite significantly underestimated, in particular for He
The present work is devoted to the performance of the random phase approximation for extended systems if singles contributions are taken into account
Summary
In the last decade the interest in many body perturbation theory has risen significantly This is to some extent related to the enormous increase in the available computer performance, but it is driven by the realization that many of the presently available density functionals have limited predictive accuracy. If the material is dominated by a single Slater determinant, the methods of choice are coupled cluster methods, as well as Møller-Plesset perturbation theory for large band gap systems. Recently these methods have become available for solids.
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