Abstract
Standard enthalpies of formation (Delta H-f(0)) of finite-length ( 5, 5) single- walled carbon nanotubes ( SWNTs) are calculated with the framework of density functional theory. Approximate expressions of (Delta H-f(0)) have been proposed for both H-terminated and C30- capped ( 5, 5) SWNTs, based upon which the calculated values of (Delta H-f(0)) have been reproduced within several kilocalories per mole. It is also found that standard enthalpies of formation contributed by per carbon, Delta H-f(0) (C), oscillate with the increment of the cluster size, suggesting the dependence of the relative stability on the axial length.