Jul 2026· Physical Chemistry, Chemical Physics - PCCP· Vol 28, pp. 18478-18490· 0 citations
Medicine
Abstract
Methylaluminoxane (MAO) is the most widely used cocatalyst for olefin polymerization, yet its molecular structure remains incompletely understood. Computational methods are essential for elucidating the structure and reactivity of MAO, but their accuracy has been difficult to assess. Benchmarking based on trimethylaluminum (TMA) dimerization has proven insufficient because it omits the oxygen environments central to MAO chemistry. Here, we benchmark 25 density functional methods against DLPNO-CCSD(T) and RI-MP2 reference calculations for a set of MAO oligomers, evaluating geometry, electronic energy, vibrational frequencies, and thermodynamic properties. We identify energetic biases toward specific structural motifs (µ4-O and µ-Me) in ten functionals, with errors ranging from under 5 kJ mol-1 to over 45 kJ mol-1. ωB97X-D4 and MN15 show the largest errors and should be avoided for pure MAO systems. Two functionals, ωB97X-V and ωB97M-D4, accurately reproduce reference electronic energies without structural bias. For vibrational properties, quasi-harmonic treatment effectively reduces method-dependent entropy variations, and thermochemical corrections prove robust across functionals. However, extending these methods to metallocene-MAO ion pairs reveals distinct system-dependent behavior that warrants further investigation. Together, these findings highlight that functional performance is system-dependent, with significant implications for computational studies of catalyst activation mechanisms.
Methylaluminoxane (MAO) is the most widely used cocatalyst in single‐site olefin polymerization, yet its molecular structures have decisively resisted characterization. Computational chemistry has played an indispensable role throughout the characterization efforts, from the earliest cage‐based structural proposals inspired by tert‐butylaluminoxane analogs through systematic hydrolysis‐based modeling to the identification of two‐dimensional sheet structures as the thermodynamically preferred motif. This review traces that computational journey, with particular attention to the methodological advances and failures that shaped it. The discovery that widely used density functional theory methods for MAO carry systematic errors for four‐coordinate aluminum–oxygen environments, and that vibrational entropy rather than electronic energy is the decisive thermodynamic quantity in the experimentally relevant size domain, fundamentally redirected the field. The resulting ovalene‐based sheet model for the dominant [(AlOMe)16(AlMe3)6Me]− anion is simultaneously consistent with electrospray ionization mass spectrometry, solid‐state NMR, X‐ray crystallography, and synchrotron pair distribution function data, and yields catalyst activation barriers in reasonable agreement with experiment. The structural foundation now established for the dominant anionic component of fresh MAO opens a realistic path toward understanding the full complexity of the MAO mixture and toward rational design of next‐generation aluminum‐based cocatalysts.
Mikko Linnolahti, Perttu Hanhisalo, Aleksi Vähäkangas· ChemPlusChem· 0 citations
We assess the accuracy of electronic structure methods for modeling the dispersion-dominated adsorption of methane, ethane, and propane, and the adsorption of hydrogen-bonded water in the Brønsted acidic zeolite chabazite (H–CHA) using density functional theory (DFT) with periodic boundary conditions and a hybrid QM:QM (QM = quantum mechanics) approach. In addition to coupled-cluster (CCSD(T)) reference energies, which agree with available experimental values within chemical accuracy limits of ±4 kJ mol–1, we also provide reference adsorption structures obtained with Møller–Plesset perturbation theory (MP2). DFT mostly overestimates binding compared to CCSD(T), with root-mean-square deviations (RMSDs) ranging from 6–29 kJ mol–1 for alkanes and 5–33 kJ mol–1 for water. QM:QM calculations with hybrid functionals as high level can reduce RMSDs from the CCSD(T) reference. With B3LYP+D4 as a high-level method, the QM:QM energies deviate by 7–12 and 11–21 kJ mol–1 for alkanes and water, respectively, depending on the low-level method. With ωB97M-V as high-level method, the RMSDs are 4–10 and 4–15 kJ mol–1, and with MP2, they are 1–3 and 2–8 kJ mol–1, respectively. When ωB97M-V is used as a high-level method or r2SCAN+D4 as a low-level method, predictions for the protonation state of water can be qualitatively wrong. For DFT modeling of periodic systems, when hybrid functionals are not affordable, we recommend revPBE+D3. For QM:QM with hybrid DFT as high-level method, ωB97M-V:revPBE+D3 is the best combination. Only CCSD(T) single points on hybrid MP2 structures reliably deliver chemically accurate adsorption energies and qualitatively correct adsorption structures.
Henning Windeck, Fabian Berger, J. Brandenburg et al.· Journal of Physical Chemistr...· 0 citations
Accurate prediction of activation barriers is essential for reliable mechanistic modeling of copper-catalyzed carbon conversion reactions yet remains challenging for conventional density functional theory. Here, we evaluate a hybrid PBE-D3/M06 approach for reaction kinetics on low-index Cu(100), Cu(110), and Cu(111) surfaces. Benchmarking against experimental barriers for seven representative elementary reactions shows that PBE-D3/M06 achieves near-chemical accuracy, with a mean absolute error and root mean square error of 0.06 eV, substantially outperforming PBE and RPBE. The method also reproduces embedded CASPT2 trends for C-C coupling on Cu(111), correctly identifying COH*-CHO* coupling as both kinetically and thermodynamically preferred. Applied to CO2 hydrogenation to methanol on Cu(111), PBE-D3/M06 indicates that the formate-mediated pathway is favored, with HCOOH* hydrogenation as the rate-determining step. This work suggests that PBE-D3/M06 is a promising framework for modeling elementary steps in copper-catalyzed carbon chemistry.
Yu Bai, Zhenbin Wang· Journal of Chemical Physics· 0 citations
Antiferromagnetically coupled bimetallic hydrides are promising catalysts for olefin hydrogenation, but their electronic structure presents a challenging problem for single-reference electronic structure methods. We investigated ethylene hydrogenation by unsupported and silica-supported dinuclear Ni and Fe hydride catalysts using density functional theory (DFT) and GPU-accelerated localized active space (LAS) multireference methods and multiconfiguration pair-density functional theory (MC-PDFT). For the unsupported dinuclear Ni hydride catalyst, different DFT functionals predict different spin-state orderings along the catalytic cycle, ethylene binding energetics, transition-state barriers, and even different rate-determining steps. In contrast, multireference methods provide a consistent description of the spin manifold and reaction energetics across the pathway, with substantially reduced sensitivity to the choice of on-top functional. The calculations further show that the bridging Ni-H-Ni motif remains intact during ethylene coordination and migratory insertion, in contrast to previously proposed mechanisms involving prior bridge opening. Comparison of supported and unsupported systems reveals strongly metal-dependent support effects. Silica coordination substantially lowers the hydride-transfer barrier in the Ni catalyst, whereas the hydrogenolysis barrier is elevated for the Fe systems. These results show that antiferromagnetically coupled bimetallic hydrides can fall outside the reliable regime of single-reference DFT and require multireference treatments to obtain consistent mechanistic predictions.
Rishu Khurana, M. Hermes, Valay Agarawal et al.· npj Computational Materials· 0 citations
This study provides a comprehensive characterization of methylxanthines in monomeric and antiparallel dimeric configurations using DFT-D3 and SAPT0 analysis. Our results elucidate a synergistic interplay between hydrogen bonding and π–π stacking, where London dispersion accounts for over 50% of the total attractive forces. The wide HOMO–LUMO gaps (7.2–9.4 eV) obtained with M06–2X and ωB97X correlate with minimal induction contributions (Eind < 9.5%) and negligible charge transfer, confirming the noncovalent nature of the assembly. A detailed thermochemical analysis confirms the spontaneity of dimerization through calculated Gibbs free energies, revealing a strong dependence on the chosen density functional. Furthermore, color-coded NCI-RDG plots provide an unambiguous mapping of attractive and steric forces, demonstrating that while dimerization preserves monomeric reactivity, it drives a stable supramolecular assembly. These insights provide a fundamental starting point for understanding the intrinsic driving forces of methylxanthines, potentially aiding in the future rational design of methylxanthine-based cocrystals and supramolecular materials.
Raúl Mendoza-Báez, D. García-Toral, A. Deriabina et al.· ACS Omega· 0 citations
Since the development of metal halide hybrid perovskite (MHP)-based solar cells, many investigations have aimed to overcome the shortcomings of the most widely used MHP, methylammonium (CH3NH3, MA) lead iodide (CH3NH3PbI3, MAPI), such as its toxicity and low stability. In this respect, many MHPs have been proposed to reduce or replace the Pb content in MAPI. This work studies the vibrational, thermodynamic, electronic, and optical properties of a proposed CH3NH3CaBr3 (MACB) cubic perovskite by using first-principles density functional theory and density functional perturbation theory to evaluate its potential as a solar cell material. The results show that MA lies stably only at certain positions within the perovskite lattice, and the barrier energy for an internal rotation to the next stable position is relatively low. Also, the mechanical properties show fragility in directions perpendicular to the C-N bond of MA. The electronic properties show a large energy gap; that is, the optical properties of MACB appear outside the ideal range for solar cell applications. These results could help understand the stabilization mechanisms of MACB and reveal its potential applications, as a computationally promising material whose optical properties are consistent with UV-protective applications in solar cells, pending experimental validation, as well as for applications as ultraviolet detectors and photonic devices such as perovskite-based light-emitting diodes.
Julio Zuriel Gonzalez-Vazquez, R. Bermeo-Campos, R. Oviedo-Roa et al.· Physical Chemistry, Chemical...· 0 citations
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