A benchmark for non-covalent interactions in solids

Abstract

A benchmark for non-covalent interactions in solids (C21) based on the experimental sublimation enthalpies and geometries of 21 molecular crystals is presented. Thermal and zero-point effects are carefully accounted for and reference lattice energies and thermal pressures are provided, which allow dispersion-corrected density functionals to be assessed in a straightforward way. Other thermal corrections to the sublimation enthalpy (the 2RT term) are reexamined. We compare the recently implemented exchange-hole dipole moment (XDM) model with other approaches in the literature to find that XDM roughly doubles the accuracy of DFT-D2 and non-local functionals in computed lattice energies (4.8 kJ/mol mean absolute error) while, at the same time, predicting cell geometries within less than 2% of the experimental result on average. The XDM model of dispersion interactions is confirmed as a very promising approach in solid-state applications.

Perspective: Fifty years of density-functional theory in chemical physics

“…The thermochemistry benchmark sets 40 that were indispensible for DFA development in the past have been joined by vdW benchmark sets. The S66 set of Rezac, Riley, and Hobza 178 for biochemical systems, the set of supramolecular complexes of Risthaus and Grimme, 179 and the molecular solids set of Otero-de-la-Roza and Johnson 180 are a few examples. Threecenter dispersion interactions, in addition to two-center interactions, are being studied.…”

Understanding the role of vibrations, exact exchange, and many-body van der Waals interactions in the cohesive properties of molecular crystals

“…For a more detailed discussion of these approximations see, e.g., Otero-de-la-Roza and Johnson. 30 The vibrational quantities can be readily calculated in the harmonic limit using DFT phonon calculations, 30,51 …”

“…Pairwise dispersion-interaction contributions were added using the DFT+vdW (or TS method), 19 using the built-in functionality of CASTEP. 41 Initial structures for the crystals were obtained either from Otero-de-la-Roza and Johnson 30 or the Cambridge Structural Database. 42 Space-group symmetry was exploited for solid-state calculations.…”

“…It is equally important to properly assess the role of the density functional used to calculate the lattice energies. While many studies have focused on the role of dispersion, 25,29,30 few have critically assessed the shortcomings of semi-local functionals in detail. For example, the de-localisation or selfinteraction errors in DFT 31 can often have a significant effect on hydrogen-bonded systems.…”

Predicting Energetics of Supramolecular Systems Using the XDM Dispersion Model

“…For the molecular crystals, backcorrected experimental sublimation enthalpies are used. 15,21,22 Despite this wealth of information, little is known about how dispersion-corrected functionals behave for relatively large (but finite) supramolecular systems; this is a question that has recently come to the forefront. 19,23,24 Specifically, it is presently unknown how the error for noncovalent binding energies using dispersion-corrected density functionals scales with system size, which is a question that is critical for applications of dispersioncorrected DFT to large complex systems, 25−28 as well as for ab initio molecular dynamics simulations.…”