“…Shows the schematic variation of (5, 5), (7, 7) and (9, 9) armchairs nanotubes. Hernandez et al (1999), Tu and Ou-Yang (2002), Wang et al (2005). The value of K extension obtained in most of previous studies (see Yakobson et al, 1996;Lu, 1997;Jin and Yuan, 2003;Wang et al, 2005;Chen and Gao, 2006;Robertson et al, 1992) mainly falls in the range of 330 to 363 J m −2 and v varies from 0.14 to 0.34.…”