Assessment of the van der Waals, Hubbard U parameter and spin‐orbit coupling corrections on the 2D/3D structures from metal gold congeners clusters

The coinage-metal clusters possess a natural complexity in their theoretical treatment that may be accompanied by inherent shortcomings in the methodological approach. Herein, we performed a scalar-relativistic density functional theory study, considering Perdew, Burke, and Ernzerhof (PBE) with (empirical and semi empirical) van der Waals (vdW), spin-orbit coupling (SOC), +U (Hubbard term), and their combinations, to treat the urn:x-wiley:01928651:media:jcc26784:jcc26784-math-0005, urn:x-wiley:01928651:media:jcc26784:jcc26784-math-0006, and urn:x-wiley:01928651:media:jcc26784:jcc26784-math-0007 clusters in different structural motifs. The energetic scenario is given by the confirmation of the 3D lowest energy configurations for urn:x-wiley:01928651:media:jcc26784:jcc26784-math-0008 and urn:x-wiley:01928651:media:jcc26784:jcc26784-math-0009 within all approaches, while for urn:x-wiley:01928651:media:jcc26784:jcc26784-math-0010 there is a 2D/3D competition, depending on the applied correction. The 2D geometry is 0.43 eV more stable with plain PBE than the 3D one, the SOC, +U, and/or vdW inclusion decreases the overestimated stability of the planar configurations, where the most surprising result is found by the D3 and D3BJ vdW corrections, for which the 3D configuration is 0.29 and 0.11 eV, respectively, more stable than the 2D geometry (with even higher values when SOC and/or +U are added). The D3 dispersion correction represents 7.9% (4.4%) of the total binding energy for the 3D (2D) configuration, (not) being enough to change the urn:x-wiley:01928651:media:jcc26784:jcc26784-math-0013 hybridization and the position of the occupied urn:x-wiley:01928651:media:jcc26784:jcc26784-math-0014-states. Our predictions are in agreement with experimental results and in line with the best results obtained for bulk systems, as well as with hybrid functionals within D3 corrections. The properties description undergoes small corrections with the different approaches, where general trends are maintained, that is, the average bond length is smaller (larger) for lower (higher)-coordinated structures, since a same number of electrons are shared by a smaller (larger) number of bonds, consequently, the bonds are stronger (weaker) and shorter (longer) and the urn:x-wiley:01928651:media:jcc26784:jcc26784-math-0015 hybridization index is larger (smaller). Thus, Au has a distinct behavior in relation to its lighter congeners, with a complex potential energy surface, where in addition to the relevant relativistic effects, correlation and dispersion effects must also be considered.

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