ABSTRACT
The effect of defect locations on the mechanical properties of armchair graphene nanoribbons (AGNRs) and the various configurations of nitrogen (N) doping on the mechanical properties of AGNRs were examined using molecular dynamics (MD) simulations. The variation of the Young's modulus (YM) and the ultimate tensile strength (UTS) of pyridinic-N, graphitic-N, and pyrrolic-N by increasing the concentration of N doping was investigated. The results of MD simulations show that the defect location has a significant effect on the UTS and failure strain (FS) of AGNRs in both vertical and horizontal directions. In the horizontal direction, variations of the UTS and FS are lower than in the vertical direction. On the other hand, the variations of the YM is almost similar in vertical and horizontal directions. The results of this work indicate that the UTS and FS of AGNRs are more sensitive than the YM of AGNRs for different defect directions. Pyridinic-N improves the mechanical properties of the defective AGNR and performs better YM and UTS values than the graphitic-N. Substitution N atoms, which are located at the defective sites and/or at the edges of AGNRs, are mechanically more favorable. Pyrrolic-N configuration has the lowest mechanical properties among the other configurations. Furthermore, pyrrolic-N with Stone-Wales-1 (SW-1) type of defect has higher mechanical properties than pyrrolic-N with Stone-Wales-2 (SW-2) type of defect.
ABSTRACT
The influence of the nitrogen (N) doping configuration on the thermal conductivity (TC) of armchair graphene nanoribbons (AGNRs) of size 15.7 nm × 7.26 nm was investigated using classical molecular dynamics (MD) simulations with the optimized Tersoff potential at room temperature. The effect of changing the N-doping site in defects on the TC of AGNRs was also investigated in detail. The variations with N concentration of the TCs of AGNRs presenting graphitic N (quarternary N), pyridinic N, and pyrrolic N doping configurations were studied. Results of MD simulations showed that, among these three doping configurations, pyridinic N was associated with the highest TC, and pyrrolic N with the lowest TC. The highest TC values were obtained when the N dopant atoms were located at the edges and at defects in the AGNR. The presence of both pyrrolic N and Stone-Wales type 1 (SW-1) defects led to a higher TC than the presence of both pyrrolic N and SW-2 defects. Phonon-defect scattering was found to be influenced by changes in C-C bond orientation. SW-1 defects were found to exert a greater influence on the TC than graphitic N doping. Furthermore, the influence on the TC of the N-doping site location in SW-1 defects was examined. Doping the central sites of SW-1 defects was found to yield higher TC values than doping the edge sites of defects. Graphitic-N doping of the more central sites in a SW-1 defect led to a higher TC than the random graphitic-N doping of sites in a SW-1 defect.
