Graphitic carbon nitride (g‐C3N4) exhibits unique properties as a support for single‐atom heterogeneous catalysts (SAHCs). Understanding how the synthesis method, carrier properties, and metal ...identity impact the isolation of metal centers is essential to guide their design. This study compares the effectiveness of direct and postsynthetic routes to prepare SAHCs by incorporating palladium, silver, iridium, platinum, or gold in g‐C3N4 of distinct morphology (bulk, mesoporous and exfoliated). The speciation (single atoms, dimers, clusters, or nanoparticles), distribution, and oxidation state of the supported metals are characterized by multiple techniques including extensive use of aberration‐corrected electron microscopy. SAHCs are most readily attained via direct approaches applying copolymerizable metal precursors and employing high surface area carriers. In contrast, although post‐synthetic routes enable improved control over the metal loading, nanoparticle formation is more prevalent. Comparison of the carrier morphologies also points toward the involvement of defects in stabilizing single atoms. The distinct metal dispersions are rationalized by density functional theory and kinetic Monte Carlo simulations, highlighting the interplay between the adsorption energetics and diffusion kinetics. Evaluation in the continuous three‐phase semihydrogenation of 1‐hexyne identifies controlling the metal–carrier interaction and exposing the metal sites at the surface layer as key challenges in designing efficient SAHCs.
Criteria are identified for preparing single‐atom heterogeneous catalysts based on carbon nitride. The impact of the synthesis route, carrier morphology, and metal identity on the speciation is determined using characterizations and simulations. Direct synthesis exploiting copolymerizable metal precursors, high mesoporosity, and the presence of defects favor the stabilization of metal atoms, but post‐synthesis approaches yield enhanced accessibility in catalyzed reactions.
The recently proposed MUonE experiment at CERN aims at providing a novel determination of the leading order hadronic contribution to the muon anomalous magnetic moment through the study of elastic ...muon-electron scattering at relatively small momentum transfer. The anticipated accuracy of the order of 10ppm demands for high-precision prediction in radiative corrections to the μe scattering as well as for robust quantitative estimates of all possible background processes. In this letter, the contribution due to the emission of a neutral pion through the process μe→μeπ0 is studied and its numerical impact is discussed in different phase space configurations by means of the upgraded Monte Carlo event generator MESMER. In fact, single π0 production could be a source of reducible background for the measurement of the QED running coupling constant at MUonE and it could be also an important background for possible New Physics searches at MUonE involving 2→3 processes, in phase space regions complementary to the ones characteristic of the elastic μe scattering.
A
bstract
We present results for the QCD next-to-leading order (NLO) calculation of single-top
t
-channel production in the 4-flavour scheme, interfaced to Parton Shower (PS) Monte Carlo programs ...according to the POWHEG and MC@NLO methods. Comparisons between the two methods, as well as with the corresponding process in the 5-flavour scheme are presented. For the first time results for typical kinematic distributions of the spectator-
b
jet are presented in an NLO + PS approach.
The MUonE experiment aims at providing a novel determination of the leading hadronic contribution to the muon anomalous magnetic moment through the study of elastic muon-electron scattering. Since ...the initial-state electrons are bound in a low-Z atomic target, the interaction between the incoming muons and the nuclei is expected to be the main source of experimental background. In this article, we study the production of a real lepton pair from the muon-nucleus scattering, discussing its numerical impact in the MUonE kinematic configuration. The process is described as a scattering of a muon in an external Coulomb field with the addition of a form factor to describe the nuclear charge distribution. The calculation is implemented in the fully differential Monte Carlo event generator Mesmer, without introducing any approximation on the angular variables.
In this paper, we study the magnetic properties of a diluted trilayer graphene structure with non-equivalent planes. The spins of the planes forming the trilayer systems ABA and BAB are S = 1 (for ...the plane A) and σ = 3/2 (for the plane B). The ground state phase diagrams are reported and discussed. Besides, we provide the variation of the total magnetizations versus reduced temperature and reduced crystal field for several values of the coupling exchange interactions and the dilution probability, using Monte Carlo simulations. The two systems provide opposite results regarding the compensation temperature Tcomp behavior as a function of dilution probability p. Indeed, the compensation temperature increases when decreasing the dilution probability for ABA system. While for the BAB system, Tcomp increases when increasing p.
•At zero temperature value, the phase diagrams corresponding to ABA and BAB systems exhibit different stable configurations.•The studied systems ABA and BAB exhibit a compensation temperature in the pure and diluted cases.•It is found that the compensation temperature increases when decreasing the dilution probability for ABA system.•In the case of BAB system, the compensation temperature decreases when decreasing the dilution probability.•For both systems (ABA and BAB), the exchange coupling effect is observed.
Inspired by the universal approximation theorem and widespread adoption of artificial neural network techniques in a diversity of fields, feed‐forward neural networks are proposed as a general ...purpose trial wave function for quantum Monte Carlo simulations of continuous many‐body systems. Whereas for simple model systems the whole many‐body wave function can be represented by a neural network, the antisymmetry condition of non‐trivial fermionic systems is incorporated by means of a Slater determinant. To demonstrate the accuracy of the trial wave functions, an exactly solvable model system of two trapped interacting particles, as well as the hydrogen dimer, is studied.
A number of general purpose trial wave functions based on feed‐forward neural networks are proposed for quantum Monte Carlo simulations of bosons and fermions. The behavior and accuracy of the trial wave functions are investigated for an exactly solvable model system of two trapped interacting particles and the hydrogen dimer.
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