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Ronaldo J. C. Batista

Bio: Ronaldo J. C. Batista is an academic researcher from Universidade Federal de Ouro Preto. The author has contributed to research in topics: Boron nitride & Graphene. The author has an hindex of 14, co-authored 56 publications receiving 590 citations. Previous affiliations of Ronaldo J. C. Batista include Universidade Federal de Minas Gerais & University of Cambridge.


Papers
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TL;DR: A physical mechanism for the effect where the combined compressive and shear stresses from the tip induce dynamical wrinkling on the upper material layers, leading to the observed flake thickening is proposed.
Abstract: We report a novel mechanical response of few-layer graphene, h-BN, and MoS(2) to the simultaneous compression and shear by an atomic force microscope (AFM) tip. The response is characterized by the vertical expansion of these two-dimensional (2D) layered materials upon compression. Such effect is proportional to the applied load, leading to vertical strain values (opposite to the applied force) of up to 150%. The effect is null in the absence of shear, increases with tip velocity, and is anisotropic. It also has similar magnitudes in these solid lubricant materials (few-layer graphene, h-BN, and MoS(2)), but it is absent in single-layer graphene and in few-layer mica and Bi(2)Se(3). We propose a physical mechanism for the effect where the combined compressive and shear stresses from the tip induce dynamical wrinkling on the upper material layers, leading to the observed flake thickening. The new effect (and, therefore, the proposed wrinkling) is reversible in the three materials where it is observed.

60 citations

Journal ArticleDOI
TL;DR: In this paper, a Monte-Carlo-based simulated annealing process combined with ab initio calculations is employed to investigate electronic and structural properties of boron nitride (BN)-doped graphene, in a wide doping range.
Abstract: A Monte-Carlo-based simulated annealing process combined with ab initio calculations is employed to investigate electronic and structural properties of boron nitride (BN)-doped graphene, in a wide doping range. We find that, for a given BN doping concentration, the doping-induced band gap can vary over an order of magnitude depending on the placement of the B and N atoms. We propose an analytical tight-binding model that reproduces the dependence of the band gap on both the concentration and the morphology obtained in the ab initio calculations and provides an upper bound for the band gap at a given BN concentration. We also predict that the dependence of the band gap with applied tensile stress should be strong, nonmonotonic, and anisotropic, within the range of strain values attainable experimentally.

56 citations

Journal ArticleDOI
TL;DR: In this paper, the morphology and optical response of annealed few-layer hexagonal boron nitride flakes deposited on a silicon substrate were studied, revealing the formation of linear wrinkles along well-defined crystallographic directions.
Abstract: Understanding layer interplay is the key to utilizing layered heterostructures formed by the stacking of different two-dimensional materials for device applications. Boron nitride has been demonstrated to be an ideal substrate on which to build graphene devices with improved mobilities. Here we present studies on the morphology and optical response of annealed few-layer hexagonal boron nitride flakes deposited on a silicon substrate that reveal the formation of linear wrinkles along well-defined crystallographic directions. The wrinkles formed a network of primarily threefold and occasionally fourfold origami-type junctions throughout the sample, and all threefold junctions and wrinkles formed along the armchair crystallographic direction. Furthermore, molecular dynamics simulations yielded, through spontaneous symmetry breaking, wrinkle junction morphologies that are consistent with both the experimental results and the proposed origami-folding model. Our findings indicate that this morphology may be a general feature of several two-dimensional materials under proper stress-strain conditions, resulting in direct consequences in device strain engineering. Open image in new window

39 citations

Journal ArticleDOI
TL;DR: In this article, first-principles calculations for the interaction of the transition metal atoms Fe, Co, and W, as well as the FeO molecule, with the boron nitride fullerene were performed.
Abstract: We perform first-principles calculations for the interaction of the transition metal atoms Fe, Co, and W, as well as the FeO molecule, with the boron nitride fullerene ${\mathrm{B}}_{36}{\mathrm{N}}_{36}$. The stable structure of the atom-fullerene complexes may have the dopant atom either at the center of the cage or making covalent bonds with the fullerene wall, with similar total energies. We also find that the FeO molecule has a binding energy with the fullerene $2.5\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ larger than those of the transition metal atoms, and that it produces larger distortions in the cage. The electronic structure changes upon doping with the presence of several gap states. No magnetic moment is induced on the BN cage and, in general, the hybrid structures have the same magnetic moments as the isolated dopants.

35 citations


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08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Journal ArticleDOI
TL;DR: Graphene and its derivatives are being studied in nearly every field of science and engineering as mentioned in this paper, and recent progress has shown that the graphene-based materials can have a profound impact on electronic and optoelectronic devices, chemical sensors, nanocomposites and energy storage.

3,118 citations