  We report combined first-principle and tight-binding (TB) calculations to
simulate the effects of chemical edge modifications on structural and
electronic properties. The C-C bond lengths and bond angles near the GNR edge
have considerable changes when edge carbon atoms are bounded to different
atoms. By introducing a phenomenological hopping parameter $t_{1}$ for
nearest-neighboring hopping to represent various chemical edge modifications,
we investigated the electronic structural changes of nanoribbons with different
widths based on the tight-binding scheme. Theoretical results show that addends
can change the band structures of armchair GNRs and even result in observable
metal-to-insulator transition.
