The recent discovery of borophene, a two-dimensional allotrope of boron, raises many questions about its structure and its chemical and physical properties. Boron has a high chemical affinity to oxygen but little is known about the oxidation behaviour of borophene. Here we use first principles calculations to study the phase diagram of free-standing, two-dimensional B 1−x O x for compositions ranging from x=0 to x=0.6, which correspond to borophene and B O 2 3 sheets, respectively. Our results indicate that no stable compounds except borophene and B O 2 3 sheets exist. Intermediate compositions are heterogeneous mixtures of borophene and B O 2 3 . Other hypothetical crystals such as B O 2 are unfavorable and some of them underwent spontaneous disproportionation into borophene and B O 2 3. It is also shown that oxidizing borophene inside the flakes is thermodynamically unfavorable over forming B O 2 3 at the edges. All findings can be rationalized by oxygen's preference of two-fold coordination which is incompatible with higher in-plane coordination numbers preferred by boron. These results agree well with recent experiments and pave the way to better understand the process of oxidation of borophene and other two-dimensional materials. OPEN ACCESS RECEIVED
Manipulating the interlayer twist angle is a powerful tool to tailor the properties of layered two-dimensional crystals. The twist angle has a determinant impact on these systems’ atomistic structure and electronic properties. This includes the corrugation of individual layers, formation of stacking domains and other structural elements, and electronic structure changes due to the atomic reconstruction and superlattice effects. However, how these properties change with the twist angle, θ, is not yet well understood. Here, we monitor the change of twisted bilayer MoS2 characteristics as a function of θ. We identify distinct structural regimes, each with particular structural and electronic properties. We employ a hierarchical approach ranging from a reactive force field through the density-functional-based tight-binding approach and density-functional theory. To obtain a comprehensive overview, we analyzed a large number of twisted bilayers with twist angles in the range of θ = 0.2° . . . 59.6°. Some systems include up to half a million atoms, making structure optimization and electronic property calculation challenging. For 13° ≤ θ ≤ 47°, the structure is well-described by a moiré regime composed of two rigidly twisted monolayers. At small twist angles (θ ≤ 3° and 57° ≤ θ), a domain-soliton regime evolves, where the structure contains large triangular stacking domains, separated by a network of strain solitons and short-ranged high-energy nodes. The corrugation of the layers and the emerging superlattice of solitons and stacking domains affects the electronic structure. Emerging predominant characteristic features are Dirac cones at K and kagome bands. These features flatten for θ approaching 0° and 60°. Our results show at which range of θ the characteristic features of the reconstruction, namely extended stacking domains, the soliton network, and superlattice, emerge and give rise to exciting electronics. We expect our findings also to be relevant for other twisted bilayer systems.
Die im Jahr 2020 aufgetretene Pandemie bedingte auch an den Universitäten einen Lockdown und die Verlagerung der Lehre in den digitalen Raum. Im Bereich der Studiengänge Chemie und Lebensmittelchemie ist dies nur teilweise möglich. Insbesondere die Laborpraktika vermitteln Kernkompetenzen, die nicht anders als in Präsenz erworben werden können. Computerpraktika hingegen können mit guter Konzeption an den heimischen Computer verlagert werden. Wir stellen hier unser Konzept vor, das es möglich gemacht hat, Computerversuche aus den Bereichen der Quantenchemie und Statistischen Thermodynamik als Lab@Home-Computerpraktikum durchzuführen. Individualisierte Aufgabenstellung, kontrollierte Vorproduktion der numerischen Ergebnisse, fortlaufende Kommunikation mit den Studierenden und umfangreiche Nutzung digitaler Lehrmethoden waren dabei die entscheidenden Grundlagen für die erfolgreiche Durchführung.
The effort for checking and correcting the spatial movement accuracy of a processing machine with 5 axes is very high. Calibration and recalibration must be carried out directly on the machine by the machine supplier or a company specializing in this. This is associated with high personnel and long machine downtimes. These constraints can be improved by using modern methods. A consistent approach of an AR-supported measurement procedure for the preparation and execution of a required measurement run and the execution of the calibration itself as a digital service is presented. This enables rapid execution by the machine operator himself using a DoubleBallBar measurement system without the need of the presence of the machine manufacturer. The determination of the calibration parameters on the basis of the measurement data is then carried out by the machine manufacturer and provided as a service. The basis for such a secure and auditable service is a digital service platform. This serves as an intermediary between the user and the machine manufacturer and uses distributed ledger technology. The approach presented is the subject of current development work.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.