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Graphene has been used as a catalyst to reduce the energy barrier for corannulene inversion. For such a catalytic study, corannulene structures are normally assumed to already be in close proximity to graphene, either in the concave-up or concave-down orientation. Here we use both the Lennard-Jones potential (pair-wise dispersion model) and density functional theory calculations to show that corannulene at a distance further away from graphene can adopt various orientations to optimise its interaction with graphene.

Abstract Retired soccer players are presenting with early onset neurodegenerative diseases, potentially from heading the ball. It has been proposed that the older composition of soccer balls places higher strains on brain tissues. The purpose of this research was to compare the dynamic head response and brain tissue strain of laboratory reconstructed headers using replicas of the 1966 Slazenger Challenge and 2018 Telstar 18 World Cup soccer balls. Head-to-ball impacts were physically conducted in the laboratory by impacting a Hybrid III head form at three locations and four velocities using dry and wet soccer ball conditions, and computational simulation was used to measure the resulting brain tissue strain. This research showed that few significant differences were found in head dynamic response and maximum principal strain between the dry 1966 and 2018 balls during reconstructed soccer headers. Headers using the wet 1966 soccer ball resulted in higher head form responses at low-velocity headers and lower head responses as velocities increased. This study demonstrates that under dry conditions, soccer ball construction does not have a significant effect on head and brain response during headers reconstructed in the laboratory. Although ball construction didn’t show a notable effect, this study revealed that heading the ball, comparable to goalkeeper kicks and punts at 22 m/s, led to maximum principal strains exceeding the 50% likelihood of injury risk threshold. This has implications for the potential risks associated with repetitive heading in soccer for current athletes.

Metal-ligand cooperation is an important aspect in earth-abundant metal catalysis. Utilizing ligands as electron reservoirs to supplement the redox chemistry of the metal has resulted in many new exciting discoveries. Here, we demonstrate that iron bipyridine-diimine (BDI) complexes exhibit an extensive electron-transfer series that spans a total of five oxidation states, ranging from the trication [Fe(BDI)]3+ to the monoanion [Fe(BDI]-1. Structural characterization by X-ray crystallography revealed the multifaceted redox noninnocence of the BDI ligand, while spectroscopic (e.g., 57Fe Mössbauer and EPR spectroscopy) and computational studies were employed to elucidate the electronic structure of the isolated complexes, which are further discussed in this report.

In this study, the gas-phase homolytic P–F and P–Cl bond dissociation energies (BDEs) of a set of thirty fluorophosphine (R1R2P–F) and thirty chlorophosphine-type (R1R2P–Cl) molecules have been obtained using the high-level W2 thermochemical protocol. For the R1R2P–F species, the P–F BDEs (at 298 K) differ by up to 117.0 kJ mol−1, with (H3Si)2P–F having the lowest BDE (439.5 kJ mol−1) and F2P–F having the largest BDE (556.5 kJ mol−1). In the case of the chlorophosphine-type molecules, the difference in BDEs is considerably smaller (i.e., 72.6 kJ mol−1), with (NC)2P–Cl having the lowest P–Cl BDE (299.8 kJ mol−1) and (HO)2P–Cl having the largest (372.4 kJ mol−1). We have further analyzed the effect of substituents in governing the P–F and P–Cl BDEs by considering the effect of substituents in the parent halogenated precursors (using molecule stabilization enthalpies) and the effect of substituents in the product radicals (using radical stabilization enthalpies). Finally, we have also assessed the performance of a wide range of DFT methods for their ability to compute the gas-phase P–F and P–Cl BDEs contained in this dataset. We find that, overall, the double hybrid functional DSD-PBEB95 offers the best performance for both bond types, with mean absolute deviations of just 2.1 (P–F BDEs) and 2.2 (P–Cl BDEs) kJ mol−1.

AbstractDifferent forms of rugby may pose distinct risks to head injury. Video of rugby match footage was analyzed using head impact magnitude, frequency, and time interval for 15s and 7s athletes. Impacts were reconstructed in laboratory, and finite element modeling was used to estimate maximum principal strain. No difference was found in impact frequency or time interval between the two forms. Significantly more head impacts of higher severity levels were documented during 7s. These findings provide objective comparisons between 7s and 15s which may guide risk mitigation strategies in managing brain trauma for specific forms of rugby. [ABSTRACT FROM AUTHOR]

We evaluate the accuracy of CCSD(T) and density functional theory (DFT) methods for the calculation of equilibrium rotational constants (Ae, Be, and Ce) for four experimentally detected low-lying C5H2 isomers (ethynylcyclopropenylidene (2), pentatetraenylidene (3), ethynylpropadienylidene (5), and 2-cyclopropen-1-ylidenethenylidene (8)). The calculated rotational constants are compared to semi-experimental rotational constants obtained by converting the vibrationally averaged experimental rotational constants (A0, B0, and C0) to equilibrium values by subtracting the vibrational contributions (calculated at the B3LYP/jun-cc-pVTZ level of the theory). The considered isomers are closed-shell carbenes, with cumulene, acetylene, or strained cyclopropene moieties, and are therefore highly challenging from an electronic structure point of view. We consider both frozen-core and all-electron CCSD(T) calculations, as well as a range of DFT methods. We find that calculating the equilibrium rotational constants of these C5H2 isomers is a difficult task, even at the CCSD(T) level. For example, at the all-electron CCSD(T)/cc-pwCVTZ level of the theory, we obtain percentage errors ≤0.4% (Ce of isomer 3, Be and Ce of isomer 5, and Be of isomer 8) and 0.9–1.5% (Be and Ce of isomer 2, Ae of isomer 5, and Ce of isomer 8), whereas for the Ae rotational constant of isomers 2 and 8 and Be rotational constant of isomer 3, high percentage errors above 3% are obtained. These results highlight the challenges associated with calculating accurate rotational constants for isomers with highly challenging electronic structures, which is further complicated by the need to convert vibrationally averaged experimental rotational constants to equilibrium values. We use our best CCSD(T) rotational constants (namely, ae-CCSD(T)/cc-pwCVTZ for isomers 2 and 5, and ae-CCSD(T)/cc-pCVQZ for isomers 3 and 8) to evaluate the performance of DFT methods across the rungs of Jacob’s Ladder. We find that the considered pure functionals (BLYP-D3BJ, PBE-D3BJ, and TPSS-D3BJ) perform significantly better than the global and range-separated hybrid functionals. The double-hybrid DSD-PBEP86-D3BJ method shows the best overall performance, with percentage errors below 0.5% in nearly all cases.

Fluoroborane-type molecules (R1R2B–F) are of interest in synthetic chemistry, but to date, apart from a handful of small species (such as H2BF, HBF2, and BF3), little is known concerning the effect of substituents in governing the strength of the B–F bonds of such species toward homolytic dissociation in the gas phase. In this study, we have calculated the bond dissociation enthalpies (BDEs) of thirty unique B–F bonds at the CCSD(T)/CBS level using the high-level W1w thermochemical protocol. The B–F bonds in all species considered are very strong, ranging from 545.9 kJ mol−1 in (H2B)2B–F to 729.2 kJ mol−1 HBF2. Nevertheless, these BDEs still vary over a wide range of 183.3 kJ mol−1. The structural properties that affect the BDEs are examined in detail, and the homolytic BDEs are rationalized based on molecule stabilization enthalpies and radical stabilization enthalpies. Since polar B–F bonds may represent a challenging test case for density functional theory (DFT) methods, we proceed to examine the performance of a wide range of DFT methods across the rungs of Jacob′s Ladder for their ability to compute B–F BDEs. We find that only a handful of DFT methods can reproduce the CCSD(T)/CBS BDEs with mean absolute deviations (MADs) below the threshold of chemical accuracy (i.e., with average deviations below 4.2 kJ mol−1). The only functionals capable of achieving this feat were (MADs given in parentheses): ωB97M-V (4.0), BMK (3.5), DSD-BLYP (3.8), and DSD-PBEB95 (1.8 kJ mol−1).

This theoretical study presents novel insights into the doping of boron clusters with an increasing number of dopant atoms, ranging from 1 to 4, that preserve the integrity of the original boron framework. The triple-chain forms of clusters B10 and B16 remain unchanged upon sequential addition of P atoms, showcasing a perfect isolobal substitution of {P} with {CH}. Similarities in the number of delocalized electrons are observed between pure and doped boron clusters, alongside the subsequent substitution of {P} with {CH}. All triple-chain structures exhibit high thermodynamic stability, having low vertical attachment energies and high vertical ionization energies. The lowest-lying isomer of B16P4 has thus a triple-chain shape instead of a tetrahedral Td form as previously reported. While AdNDP analysis confirms the number of globally delocalized electrons, it differs much from a previous interpretation. The magnetic ring current maps support the double aromaticity of triple-chain structures. Electron counting rules established for triple-chain structures are verified. The particle-in-a-rectangular-box model elucidates the relationship between the structure size and electron configuration and aids in understanding the transition from antiaromatic to aromatic configurations. The self-locking phenomenon is crucial for adhering to the triple-chain model and satisfying electron configuration requirements. [ABSTRACT FROM AUTHOR]

Introduction I. Remote Arbitration Hearings in 2020: The Legalities and the Practicalities II. Remote Hearings as the Present and Future of Commercial Arbitration III. Beyond Commercial Arbitration Introduction If any [...], Commercial arbitration, like litigation, was forced by the pandemic to resort to remote proceedings. The arbitration community had both the capacity and the motivation to go remote, and did so at remarkable speed. However, it is unclear how durable these emergency adaptations will be--are remote hearings a new normal, or a crisis response that will fade along with the pandemic? The author argues that remote hearings are indeed here to stay. The experience of commercial arbitration in 2020 shows that the cost and accessibility benefits provided by remote hearings are significant, and that most of the concerns either have practical fixes or evaporate with greater familiarity. Remote hearings neither will nor should become universal, but will likely be a default option in arbitration, especially for international disputes. Nevertheless, planning, vigilance, and a commitment to expend sufficient resources are needed to make remote hearings accessible, effective, and fair. The author concludes by listing five lessons that other forms of dispute resolution, in particular litigation, can learn from the experience of commercial arbitration during the pandemic: (i) attention to the technical setup is vital, (ii) the necessary infrastructure is not cheap and the costs are ongoing (iii) remote hearings are not an all-or-nothing matter, (iv) their greater flexibility makes it possible to customize procedures for each dispute, and (v) frequent breaks are necessary.

[5.5.5.5]hexaene is a [12]annulene ring with a symmetrically bound carbon atom in its center. This is the smallest hydrocarbon with a hyperbolic paraboloid shape. [5.5.5.5]hexaene and related hydrocarbons are important building blocks in organic and materials chemistry. For example, penta-graphene—a puckered 2D allotrope of carbon—is comprised of similar repeating subunits. Here, we investigate the thermochemical and kinetic properties of [5.5.5.5]hexaene at the CCSD(T) level by means of the G4 thermochemical protocol. We find that this system is energetically stable relative to its isomeric forms. For example, isomers containing a phenyl ring with one or more acetylenic side chains are higher in energy by ∆H298 = 17.5–51.4 kJ mol−1. [5.5.5.5]hexaene can undergo skeletal inversion via a completely planar transition structure; however, the activation energy for this process is ∆H‡298 = 249.2 kJ mol−1 at the G4 level. This demonstrates the high configurational stability of [5.5.5.5]hexaene towards skeletal inversion. [5.5.5.5]hexaene can also undergo a π-bond shift reaction which proceeds via a relatively low-lying transition structure with an activation energy of ∆H‡298 = 67.6 kJ mol−1. Therefore, this process is expected to proceed rapidly at room temperature.

High-level double-hybrid DFT simulations reveal that strong hydrogen-bond-donor catalysts (e.g., ethylene glycol, guanidine, and thiourea) significantly accelerate the migration of epoxy oxygen on the surface of graphene oxide, enhancing the reaction rate by 6–12 orders of magnitude. These results shed light on previously puzzling experimental observations. [ABSTRACT FROM AUTHOR]

The isomerisation energies and thermal stabilities of the entire set of C40 fullerene isomers are investigated using molecular dynamics simulations with the recently developed machine-learning-based Gaussian Approximation Potential (GAP-20) force field. Our simulations predict high statistical correlation between the relative isomerisation energy distribution of all C40 isomers and their thermal fragmentation temperatures. The most energetically and thermally stable isomer is the symmetric C40-D2 isomer and its fragmentation temperature is 3875 ± 25 K. In contrast, the least stable isomer is the D5d nanorod-shaped isomer which is 146.8 kcal mol−1 higher in energy and decomposes at 2975 ± 25 K, i.e., around 900 K below the most stable isomer. In addition, we show that most isomers lie in the range between 20 and 60 kcal mol−1 above the most stable isomer, and nearly 60% of isomers decompose in the temperature range of 3425–3675 K. These computational results provide valuable insights into the synthesis of C40 fullerenes at high-temperatures.