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Pascale, F.; D'Arco, P.; Lebègue, S.; Dovesi, R.
doi: 10.1002/jcc.27306pmid: 38217380
The KScF 3 perovskite has been used as a model for investigating the relative importance of the Jahn‐Teller (JT) lift of degeneracy, the ScF 6 octahedra rotation (OR), and the quadrupole‐quadrupole interaction linked to different occupancy of the Sc t 2g subshell in various sites of the unit cell (orbital ordering, OO). The group‐subgroup sequence Pm3¯m, P4mmm, P4mbm, and Pnma, supplemented by Cmmm and I4mcm, has been explored by using an all electron Gaussian type basis set, hybrid functionals, and the CRYSTAL17 code. The JT lift of degeneracy provides a stabilization about 5 times larger than the sum of the OO and OR effects. The energy gained in the transition from P4mmm to P4mbm, consisting in a rotation of the octahedra around the c axis, is 1077 μE h. From P4mbm to Pnma, additional rotations around the a and b axes are possible, and the d Sc electron can occupy a different t 2g orbital, with a total energy reduction of 2318 μE h. The rotation of the octahedra reduces the strength of superexchange: in going from P4mmm to Pnma the G‐AFM stabilization with respect to FM shrinks by a factor 4.
Shaalan Alag, Ahmed; Szalay, Péter G.; Tajti, Attila
doi: 10.1002/jcc.27307pmid: 38241483
The electronic excitations of conformationally constrained bithiophene cage systems as previously investigated by Lewis et al. (J. Am. Chem. Soc. 143, 18548 (2021)) are revisited, employing the correlated ab initio Scaled Opposite‐Spin Algebraic Diagrammatic Construction Second Order electronic structure method. Quantitative descriptors are determined to assess the extent of charge transfer between the bithiophene moieties and the capping domains, represented by either phenyl or triazine groups. The investigation substantiates intrinsic differences in the photophysical behavior of these two structural variants and reveals the presence of lower‐energy excited states characterized by noteworthy charge transfer contributions in the triazine cage system. The manifestation of this charge transfer character is discernible even at the Franck–Condon geometry, persisting throughout the relaxation of the excited state. By examining isolated monomer building blocks, we confirm the existence of analogous charge transfer contributions in their excitations. Employing this methodological approach facilitates the prospective identification of potential wall/cap chromophore pairs, wherein charge transfer pathways can be accessed within the energetically favorable regime.
Mondal, Himangshu; Chattaraj, Pratim Kumar
doi: 10.1002/jcc.27285pmid: 38261518
CO2 reduction is appealing for the long‐term production of high‐value fuels and chemicals. Herein, using density functional theory (DFT) based calculations, we study the CO2 reduction pathway to formic acid using aluminum hydride and phosphine derivatives. Our primary focus is on aluminum hydride derivatives, aimed at improving the efficiency of the CO2 reduction process. Substituents with σ‐donating properties at the aluminum center are discovered to lower the activation barriers. We demonstrate how di‐tert‐butylphosphine oxide (LB‐O)/di‐tert‐butylphosphine sulfide (LB‐S)/di‐tert‐butylphosphanimine (LB‐N) work together with aluminum hydride to facilitate CO2 reduction process and generate in‐situ frustrated Lewis pairs (FLPs), such as FLP‐O, FLP‐S, and FLP‐N. The activation strain model (ASM) analysis reveals the significance of strain energy in determining activation barriers. EDA‐NOCV and PIO analyses elucidate the orbital interactions at the corresponding transition states. Furthermore, the study delves into the activation of various small molecules, such as dihydrogen, acetylene, ethylene, carbon dioxide, nitrous oxide, and acetonitrile, using those in‐situ generated FLPs. The study highlights the low activation barriers and emphasizes the potential for small molecule activation in this context.
Achazi, Andreas J.; Fataj, Xhesilda; Rohland, Philip; Hager, Martin D.; Schubert, Ulrich S.; Mollenhauer, Doreen
doi: 10.1002/jcc.27299pmid: 38258532
Benzo[d]‐X‐zolyl‐pyridinyl (XO, S, NH) radicals represent a promising class of redox‐active molecules for organic batteries. We present a multistep screening procedure to identify the most promising radical candidates. Experimental investigations and highly correlated wave function‐based calculations are performed to determine benchmark redox potentials. Based on these, the accuracies of different methods (semi‐empirical, density functional theory, wave function‐based), solvent models, dispersion corrections, and basis sets are evaluated. The developed screening procedure consists of three steps: First, a conformer search is performed with CREST. The molecules are selected based on the redox potentials calculated using GFN2‐xTB. Second, HOMO energies calculated with reparametrized B3LYP‐D3(BJ) and the def2‐SVP basis set are used as selection criteria. The final molecules are selected based on the redox potentials calculated from Gibbs energies using BP86‐D3(BJ)/def2‐TZVP. With this multistep screening approach, promising molecules can be suggested for synthesis, and structure–property relationships can be derived.
Bodo, Filippo; Erba, Alessandro; Kraka, Elfi; Moura, Renaldo T.
doi: 10.1002/jcc.27311pmid: 38279637
The Local Vibrational Mode Analysis, initially applied to diverse molecular systems, was extended to periodic systems in 2019. This work introduces an enhanced version of the LModeA software, specifically designed for the comprehensive analysis of two and three‐dimensional periodic structures. Notably, a novel interface with the Crystal package was established, enabling a seamless transition from molecules to periodic systems using a unified methodology. Two distinct sets of uranium‐based systems were investigated: (i) the evolution of the Uranyl ion (UO 22+) traced from its molecular configurations to the solid state, exemplified by Cs 2UO 2Cl 4 and (ii) Uranium tetrachloride (UCl 4) in both its molecular and crystalline forms. The primary focus was on exploring the impact of crystal packing on key properties, including IR and Raman spectra, structural parameters, and an in‐depth assessment of bond strength utilizing local mode perspectives. This work not only demonstrates the adaptability and versatility of LModeA for periodic systems but also highlights its potential for gaining insights into complex materials and aiding in the design of new materials through fine‐tuning.
Kalayan, Jas; Ramzan, Ismaeel; Williams, Christopher D.; Bryce, Richard A.; Burton, Neil A.
doi: 10.1002/jcc.27313pmid: 38284556
Molecular simulations have become a key tool in molecular and materials design. Machine learning (ML)‐based potential energy functions offer the prospect of simulating complex molecular systems efficiently at quantum chemical accuracy. In previous work, we have introduced the ML‐based PairF‐Net approach to neural network potentials, that adopts a pairwise interatomic scheme to predicting forces within a molecular system. Here, we further develop the PairF‐Net model to intrinsically incorporate energy conservation and couple the model to a molecular mechanical (MM) environment within the OpenMM package. The updated PairF‐Net model yields energy and force predictions and dynamical distributions in good agreement with the rMD17 dataset of ten small organic molecules in the gas‐phase. We further show that these in vacuo ML models of small molecules can be applied to force predictions in aqueous solution via hybrid ML/MM simulations. We present a new benchmark dataset for these ten molecules in solution, obtained from QM/MM simulations, which we denote as rMD17‐aq (https://zenodo.org/records/10048644); and assess the ability of PairF‐Net to reproduce the molecular energy, atomic forces and dynamical distributions of these solution conformations via ML/MM simulations.
Barrera, Yoshio; Anderson, James S. M.
doi: 10.1002/jcc.27314pmid: 38299704
The reactivity of 22 unsaturated molecules undergoing attack by a methyl radical (⋅CH3) have been elucidated using the condensed radical general‐purpose reactivity indicator (condensed radical GPRI) appropriate for relatively nucleophilic or electrophilic molecules. Using the appropriate radical GPRI equation for electrophilic attack or nucleophilic radical attack, seven different population schemes were used to assign the most reactive atoms in each of the 22 molecules. The results show that the condensed radical GPRI is sensitive to the population scheme chosen, but less sensitive than the radical Fukui function. Therefore, the reliability of these methods depends on the population scheme. Our investigation indicates that the condensed radical GPRI is most accurate in predicting the dominant products of the methyl radical addition reactions on a variety of unsaturated molecules when the Hirshfeld, Merz–Singh–Kollman, or Voronoi deformation density population schemes are used. Furthermore, for all populations schemes in the majority of instances where the radical Fukui function failed the radical GPRI was able to identify the most reactive atom under certain reactivity conditions.
Showing 1 to 10 of 12 Articles
A series of pentagonal bipyramidal anionic germanium clusters doped with heavy rare earth elements, REGe6− (RE = Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), have been identified at the PBE0/def2‐TZVP level using density functional theory (DFT). Our findings reveal that the centrally doped pentagonal ring structure demonstrates enhanced stability and heightened aromaticity due to its uniform bonding characteristics and a larger charge transfer region. Through natural population analysis and spin density diagrams, we observed a monotonic decrease in the magnetic moment from Gd to Yb. This is attributed to the decreasing number of unpaired electrons in the 4f orbitals of the heavy rare earth atoms. Interestingly, the system doped with Er atoms showed lower stability and anti‐aromaticity, likely due to the involvement of the 4f orbitals in bonding. Conversely, the systems doped with Gd and Tb atoms stood out for their high magnetism and stability, making them potential building blocks for rare earth‐doped semiconductor materials.