Exploring pentagon-heptagon pair defects in the triangular graphene quantum dots: A computational study

We have applied density functional calculations to investigate Stone Wales (SW) and carbon ad-dimer (CD) defect formation in triangular graphene quantum dots (GQDs). According to our results, defect formation energies depend on the positions of SW defects, such that the rotation of the C−C bond located near the vertex of triangular GQD is easier than the rotation of other C−C bonds. Therefore, the multiply defective GQDs with isolated SW defect sites are the most favorable while the formation of pentalene like structures in the connected SW defect sites costs larger formation energies. Introducing of carbon dimer defects on a triangular GQD induces a curvature at the defective sites, which leads to a more complex defect configuration with cone-like structure in the CD defective GQD with three defective sites. Then, formation energies for CD defective GQDs are higher than those for SW defective ones. The electrophilicity values calculated for SW and CD defective GQDs are greater than those for pristine GQDs. Moreover, perturbation of strong sp² bonding network of graphitic carbons on the GQD, leading to the formation of more localized C−C bonds, results in further electron deficiency of multiply SW and CD defective GQDs with increasing of electrophilicity values. - Highlights: • Defect formation energy depends on positions of SW defects. • Defective GQDs with isolated SW defects are the most favorable. • Introducing of CD defects induces a curvature leading to cone-like structure. • Defect formation energies for CD defective GQDs are higher than those for SW ones. • Electrophilicity: CD defective GQDs > SW defective GQDs > perfect GQDs.