**Stiffness and strength of oxygen-functionalized graphene with vacancies**

A Zandiatashbar and E Ban and RC Picu, JOURNAL OF APPLIED PHYSICS, 116, 184308 (2014).

DOI: 10.1063/1.4901580

The 2D elastic modulus (E-2D) and strength (sigma(2D)) of defective graphene sheets containing vacancies, epoxide, and hydroxyl functional groups are evaluated at 300K by atomistic simulations. The fraction of vacancies is controlled in the range 0% to 5%, while the density of functional groups corresponds to O:C ratios in the range 0% to 25%. In- plane modulus and strength diagrams as functions of vacancy and functional group densities are generated using models with a single type of defect and with combinations of two types of defects (vacancies and functional groups). It is observed that in models containing only vacancies, the rate at which strength decreases with increasing the concentration of defects is largest, followed by models containing only epoxide groups and those with only hydroxyl groups. The effect on modulus of vacancies and epoxides present alone in the model is similar, and much stronger than that of hydroxyl groups. When the concentration of defects is large, the combined effect of the functional groups and vacancies cannot be obtained as the superposition of individual effects of the two types of defects. The elastic modulus deteriorates faster (slower) than predicted by superposition in systems containing vacancies and hydroxyl groups (vacancies and epoxide groups). (C) 2014 AIP Publishing LLC.

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