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Because of instability issues presented by metal halide perovskites based on methylammonium (MA), its replacement to Cs has emerged as an alternative to improve the materials' durability. However, the impact of this replacement on electronic properties, especially gap energy and bulk Rashba splitting remains unclear since electrostatic interactions from organic cations can play a crucial role. Through first‐principles calculations, we investigated how organic/inorganic cations impact the electronic properties of MAPbI3 and CsPbI3 perovskites. Although at high temperatures the organic cation can assume spherical‐like configurations due to its rotation into the cages, our results provide a complete electronic mechanism to show, from a chemical perspective based on ab initio calculations at 0K, how the MA dipoles suppression can reduce the MAPbI3 gap energy by promoting a degeneracy breaking in the electronic states from the PbI3 framework, while the dipole moment reinforcement is crucial to align theory ↔ experiment, increasing the bulk Rashba splitting through higher Pb off‐centering motifs. The lack of permanent dipole moment in Cs results in CsPbI3 polymorphs with a pronounced Pb on‐centering‐like feature, which causes suppression in their respective bulk Rashba effect. [ABSTRACT FROM AUTHOR]

Gold and silver subnanoclusters with few atoms are prominent candidates for catalysis‐related applications, primarily because of the large fraction of lower‐coordinated atoms exposed and ready to interact with external chemical species. However, an in‐depth energetic analysis is necessary to characterize the relevant terms within the molecular adsorption process that can frame the interactions within the Sabatier principle. Herein, we investigate the interaction between Agn and Aun subnanoclusters (clu, n = 2–7) and N2, NO, CO, and O2 molecules, using scalar‐relativistic density functional theory calculations within van der Waals D3 corrections. The onefold top site is preferred for all chemisorption cases, with a predominance of linear (≈180°) and bent (≈120°) molecular geometries. A larger magnitude of adsorption energy is correlated with smaller distances between molecules and clusters and with the weakening of the adsorbates bond strength represented by the increase of the equilibrium distances and decrease of molecular stretching frequencies. From the energetic decomposition, the interaction energy term was established as an excellent descriptor to classify subnanoclusters in the adsorption/desorption process concomitant with the Sabatier principle. The limiting cases: (i) weak molecular adsorption on the subnanoclusters, which may compromise the reaction activation, where an interaction energy magnitude close to 0 eV is observed (e.g., physisorption in N2/Ag6); and (ii) strong molecular interactions with the subnanoclusters, given the interaction energy magnitude is larger than at least one of the individual fragment binding energies (e.g., strong chemisorption in CO/Au4 and NO/Au4), conferring a decrease in the desorption rate and an increase in the possible poisoning rate. However, the intermediate cases are promising by involving interaction energy magnitudes between zero and fragment binding energies. Following the molecular closed‐shell (open‐shell) electronic configuration, we find a predominant electrostatic (covalent) nature of the physical interactions for N2 ⋯clu and CO ⋯clu (O2⋯clu and NO⋯clu), except in the physisorption case (N2/Ag6) where dispersive interaction is dominant. Our results clarify questions about the molecular adsorption on subnanoclusters as a relevant mechanistic step present in nanocatalytic reactions. [ABSTRACT FROM AUTHOR]

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 Cu13, Ag13, and Au13 clusters in different structural motifs. The energetic scenario is given by the confirmation of the 3D lowest energy configurations for Cu13 and Ag13 within all approaches, while for Au13 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 sd hybridization and the position of the occupied d‐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 sd 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. [ABSTRACT FROM AUTHOR]