Graphyne Oxidation: Insights From a Reactive Molecular Dynamics Investigation
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Graphyne Oxidation: Insights From a Reactive Molecular Dynamics Investigation L. D. Machado1, P. A. S. Autreto1 and D. S. Galvao1. 1
Applied Physics Department, State University of Campinas, 13083-970, Campinas, São Paulo, Brazil. ABSTRACT Graphyne is a generic name for a family of carbon allotrope two-dimensional structures where sp2 (single and double bonds) and sp (triple bonds) hybridized states coexists. They exhibit very interesting electronic and mechanical properties sharing some of the unique graphene characteristics. Similarly to graphene, the graphyne electronic properties can be modified by chemical functionalization, such as; hydrogenation, fluorination and oxidation. Oxidation is of particular interest since it can produce significant structural damages. In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics and structural changes of the oxidation of single-layer graphyne membranes at room temperature. We have considered Į, ȕ, and Ȗ-graphyne structures. Our results showed that the oxidation reactions are strongly site dependent and that the sp-hybridized carbon atoms are the preferential sites to chemical attacks. Our results also showed that the effectiveness of the oxidation (estimated from the number of oxygen atoms covalently bonded to carbon atoms) follows the Į, ȕ, Ȗ-graphyne structure ordering. These differences can be explained by the fact that for Į-graphyne structures the oxidation reactions occur in two steps: first, the oxygen atoms are trapped at the center of the large polygonal rings and then they react with the carbon atoms composing of the triple bonds. The small rings of Ȗ-graphyne structures prevent these reactions to occur. The effectiveness of ȕ-graphyne oxidation is between the Į- and Ȗ-graphynes. INTRODUCTION Carbon-based materials of reduced dimensionality have shown to exhibit some extraordinary structural, thermal and electronic properties. One example of this is graphene [1], a single-planar layer of sp2-hybridized carbons that has become one of the hottest topics in materials science today. Due to its unique properties graphene is considered as the basis for a new nanoelectronics [1-3]. However, in its pristine form graphene is a zero bandgap semiconductor, which limits its use in transistor applications [3]. Diverse physical and chemical approaches have been tried to solve this problem [4-6]. Ideally, the gap opening should not compromise other desirable electronic properties, such as, the linear dependence of the energy of the conduction and valence electrons with their momentum, i. e., the main Dirac cone properties. With the approaches mentioned above this has been only partially achieved [1-6]. In part because of this, there is a renewed interest in other possible 2D carbon-based structures, as for example, the graphyne structures (Figure 1) [7,8]. These structures were proposed by Baughman and co-workers [7] and structurally are composed of polygonal rings
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composed of carbon atoms with the simultaneous ex
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