OICC Press International Journal of Nano Dimension 2228-5059 2 4 2024 03 01 Preparation and investigation of the adsorption effects of CO2 on the hardness of the SWCNT (8,0) by gap HOMO-LUMO 10.7508/ijnd.2011.04.010 EN Kh. Tavakoli Chemistry Department, Islamic Azad University-, Shahrekord Branch, Shahrekord, Iran. M. Keshavarz Islamic Azad University, shahreza Branch, Isfahan, Iran Chemistry Department, shahreza University, P O Box 311-86145, Isfahan, Iran. A. Kazemi Chemistry Department, Islamic Azad University-, Shahrekord Branch, Shahrekord, Iran. Journal Article 2024 03 01 In this study the hardness SWCT was calculated with B3LYP,HF method and 3-21G,6-31G,6-311G basis set .Then it was investigated with the best method(B3LYP) and basis set(6-31G) to study the adsorption effects CO2 on the hardness of SWCNT with gap HOMO-LUMO in two shape: Horizontal, Vertical and Top-Center-Bridge and We also provide the effects of CO2 adsorption on the electronic properties(DOS) of the CNTs. The soft wares which were used in this study were Gaussian 03w; Gauss view 5.0w and Nano tub modeler. The Purpose of this study is to compare the effects of the basis set&CO2 adsorption on the hardness of SWCNT (8, 0) in gases phase.