Recent theoretical proposals suggest that strain can be used to engineer graphene electronic states through the creation of a pseudo-magnetic field. This effect is unique to graphene because of its ...massless Dirac fermion-like band structure and particular lattice symmetry (C₃v). Here, we present experimental spectroscopic measurements by scanning tunneling microscopy of highly strained nanobubbles that form when graphene is grown on a platinum (111) surface. The nanobubbles exhibit Landau levels that form in the presence of strain-induced pseudo-magnetic fields greater than 300 tesla. This demonstration of enormous pseudo-magnetic fields opens the door to both the study of charge carriers in previously inaccessible high magnetic field regimes and deliberate mechanical control over electronic structure in graphene or so-called "strain engineering."
Display omitted
•A new PAW data-set and US pseudopotential library is described.•All elements from H to Pu are considered.•Scalar relativistic and fully relativistic data sets are presented.•The ...choices made for the pseudopotential construction are critically discussed.•The library is compared on a large set of solids with the GBRV library.
We discuss the generation of a library of projector augmented-wave (PAW) and ultrasoft pseudopotentials (PPs) for all elements of the periodic table from H to Pu. The PPs are compared with two libraries: pslibrary.0.3.1 and the GBRV library (Garrity et al., 2013). The PPs are tested on the lattice constants of the fcc and bcc structures of the 63 elements of the GBRV library. The same parameters are used to generate fully relativistic PPs that are compared with the scalar relativistic PPs. The PPs of lanthanides and actinides are tested on all-electron data available in the literature.
We use scanning tunneling microscopy and X-ray spectroscopy to characterize the atomic and electronic structure of boron-doped and nitrogen-doped graphene created by chemical vapor deposition on ...copper substrates. Microscopic measurements show that boron, like nitrogen, incorporates into the carbon lattice primarily in the graphitic form and contributes ~0.5 carriers into the graphene sheet per dopant. Density functional theory calculations indicate that boron dopants interact strongly with the underlying copper substrate while nitrogen dopants do not. The local bonding differences between graphitic boron and nitrogen dopants lead to large scale differences in dopant distribution. The distribution of dopants is observed to be completely random in the case of boron, while nitrogen displays strong sublattice clustering. Structurally, nitrogen-doped graphene is relatively defect-free while boron-doped graphene films show a large number of Stone-Wales defects. These defects create local electronic resonances and cause electronic scattering, but do not electronically dope the graphene film.
In monolayer graphene, substitutional doping during growth can be used to alter its electronic properties. We used scanning tunneling microscopy, Raman spectroscopy, x-ray spectroscopy, and first ...principles calculations to characterize individual nitrogen dopants in monolayer graphene grown on a copper substrate. Individual nitrogen atoms were incorporated as graphitic dopants, and a fraction of the extra electron on each nitrogen atom was delocalized into the graphene lattice. The electronic structure of nitrogen-doped graphene was strongly modified only within a few lattice spacings of the site of the nitrogen dopant. These findings show that chemical doping is a promising route to achieving high-quality graphene films with a large carrier concentration.
The Chronus Quantum (ChronusQ) software package is an open source (under the GNU General Public License v2) software infrastructure which targets the solution of challenging problems that arise in ab ...initio electronic structure theory. Special emphasis is placed on the consistent treatment of time dependence and spin in the electronic wave function, as well as the inclusion of relativistic effects in said treatments. In addition, ChronusQ provides support for the inclusion of uniform finite magnetic fields as external perturbations through the use of gauge‐including atomic orbitals. ChronusQ is a parallel electronic structure code written in modern C++ which utilizes both message passing implementation and shared memory (OpenMP) parallelism. In addition to the examination of the current state of code base itself, a discussion regarding ongoing developments and developer contributions will also be provided.
This article is categorized under:
Software > Quantum Chemistry
Electronic Structure Theory > Ab Initio Electronic Structure Methods
Electronic Structure Theory > Density Functional Theory
The Chronus Quantum (ChronusQ) software package is an electronic structure software package specializing in time dependent and relativistic electronic structure theory written in modern C++.
As a sustainable technology, semiconductor photocatalysis has attracted considerable interest in the past several decades owing to the potential to relieve or resolve energy and ...environmental‐pollution issues. By virtue of their unique structural and electronic properties, emerging ultrathin 2D materials with appropriate band structure show enormous potential to achieve efficient photocatalytic performance. Here, the state‐of‐the‐art progress on ultrathin 2D photocatalysts is reviewed and a critical appraisal of the classification, controllable synthesis, and formation mechanism of ultrathin 2D photocatalysts is presented. Then, different strategies to tailor the electronic structure of ultrathin 2D photocatalysts are summarized, including component tuning, thickness tuning, doping, and defect engineering. Hybridization with the introduction of a foreign component and maintaining the ultrathin 2D structure is presented to further boost the photocatalytic performance, such as quantum dots/2D materials, single atoms/2D materials, molecular/2D materials, and 2D–2D stacking materials. More importantly, the advancement of versatile photocatalytic applications of ultrathin 2D photocatalysts in the fields of water oxidation, hydrogen evolution, CO2 reduction, nitrogen fixation, organic syntheses, and removal pollutants is discussed. Finally, the future opportunities and challenges regarding ultrathin 2D photocatalysts to bring about new opportunities for future research in the field of photocatalysis are also presented.
Recent progress in the study of ultrathin 2D photocatalysts is reviewed. Different strategies to tailor the electronic structures and hybridizations while maintaining the ultrathin 2D structure to further boost the photocatalytic activity are presented. The advancement of versatile photocatalytic applications of ultrathin 2D photocatalysts is also discussed.
PDF
