Despite the frequent use of noble gas ion irradiation of graphene, the atomistic-scale details, including the effects of dose, energy, and ion bombardment species on defect formation, and the associated dynamic processes involved in the irradiations and subsequent relaxation have not yet been thoroughly studied. Here, we simulated the irradiation of graphene with noble gas ions and the subsequent effects of annealing. Lattice defects, including nanopores, were generated after the annealing of the irradiated graphene, which was the result of structural relaxation that allowed the vacancy-type defects to coalesce into a larger defect. Larger nanopores were generated by irradiation with a series of heavier noble gas ions, due to a larger collision cross section that led to more detrimental effects in the graphene, and by a higher ion dose that increased the chance of displacing the carbon atoms from graphene. Overall trends in the evolution of defects with respect to a dose, as well as the defect characteristics, were in good agreement with experimental results. Additionally, the statistics in the defect types generated by different irradiating ions suggested that the most frequently observed defect types were Stone-Thrower-Wales (STW) defects for He(+) irradiation and monovacancy (MV) defects for all other ion irradiations.
Despite its importance, the mechanical behavior of graphene under the impact of projectiles has rarely been studied due to experimental and computational difficulties. Here, we simulated the impact of silica and nickel projectiles with a supersonic initial velocity on graphene. Then we analyzed the impact by using ReaxFF reactive force field method, which is capable of describing the entire system. During the process of projectile penetration, we identified various atomistic features, such as the formation of pentagon/heptagon pairs at the *) also were addressed. The values of E p * obtained in our simulations were in general agreement with the recent experimental values reported by Lee et al. [Science 2014, 346, (6213), 1092-1096]. Our simulation results showed that E p * was correlated with the diameter of maximum deformation of graphene before crack initiation, demonstrating the superior E p * of graphene as a result of its high ultimate stress and strain.
Bismuth electrodes undergo distinctive electrochemically induced structural changes in nonaqueous imidazolium ([Im] + )-based ionic liquid solutions under cathodic polarization. In situ X-ray reflectivity (XR) studies have been undertaken to probe well-ordered Bi (001) films which originally contain a native Bi 2 O 3 layer. This oxide layer gets reduced to Bi 0 during the first cyclic voltammetry (CV) scan in acetonitrile solutions containing 1-butyl-3-methylimidazolium ([BMIM] + ) electrolytes. Approximately 60% of the Bi (001) Bragg peak reflectivity is lost during a potential sweep between −1.5 and −1.9 V vs Ag/AgCl due to a ∼ 4−10% thinning and a ∼40% decrease in lateral size of Bi (001) domains, which are mostly reversed during the anodic scan. Repeated potential cycling enhances the thinning and roughening of the films, suggesting that partial dissolution of Bi ensues during negative polarization. The mechanism of this behavior is understood through molecular dynamics simulations using ReaxFF and density functional theory (DFT) calculations. Both approaches indicate that [Im] + cations bind to the metal surface more strongly than tetrabutylammonium (TBA + ) as the potential and the charge on the Bi surface become more negative. ReaxFF simulations predict a higher degree of disorder for a negatively charged Bi (001) slab in the presence of the [Im] + cations and substantial migration of Bi atoms from the surface. DFT simulations show the formation of Bi•••[Im] + complexes that lead to the dissolution of Bi atoms from step edges on the Bi (001) surface at potentials between −1.65 and −1.95 V. Bi desorption from a flat terrace requires a potential of approximately −2.25 V. Together, these results suggest the formation of a Bi•••[Im] + complex through partial cathodic corrosion of the Bi film under conditions (potential and electrolyte composition) that favor the catalytic reduction of CO 2 .
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.