DFT study of the formation of CH2=CF2 through both methylene insertion and b-fluoride elimination on the Ag(111) surface
學年 92
學期 2
出版（發表）日期 2004-04-01
作品名稱 DFT study of the formation of CH2=CF2 through both methylene insertion and b-fluoride elimination on the Ag(111) surface
作品名稱（其他語言）
著者 林志興; Lin, Jyh-shing; Chou, Wen-Chi
單位 淡江大學化學學系
出版者 World Scientific Publishing
著錄名稱、卷期、頁數 Surface review and letter11(2), pp.229-234
摘要 Total energy calculations based on (1) density functional theory (DFT) in connection with ultrasoft pseudopotential and generalized gradient spin-polarized approximation (GGSA) and (2) the partial structural constraint path minimization (PSCPM) method have been used to investigate the energetically more favorable pathway for methylene (CH2) insertion into the Ag–CF3 bond followed by β-fluoride elimination to generate an isolated CH2=CF2(g) above the Ag(111) surface. The diffusion of the fcc-hollow site of CF3(ads) toward the bridge site of CH2(ads) is proposed as an energe*tically more favorable path for CH2 insertion into the Ag–CF3 bond to form the bridge site of CH2CF3(ads) on the Ag(111) surface. Then we proceed with β-fluoride elimination to form an isolated CH2=CF2(g) and the bridge site of F(ads) on the Ag(111) surface. Our calculated energy barrier for β-fluoride elimination is 0.715 eV higher than that for CH2 insertion on the Ag(111) surface. These calculated results imply that β-fluoride elimination rather than CH2 insertion on the Ag(111) surface controls the CH2=CF2(g) formation rate as observed from temperature-programmed reaction (TPR) experimental data. Finally, we attribute these different energy barriers to the different transition state structures — largely distorted seven-centered versus less distorted four-centered — involved in these two different processes.
關鍵字 Fischer–Tropsch process;Ag(111) surface;ultrasoft pseudopotential;density functional theory;temperature-programmed reaction;generalized gradient spin-polarized approximation
語言 en
ISSN 0218-625X
期刊性質 國內
收錄於
產學合作
通訊作者
審稿制度 否
國別 TWN
公開徵稿
出版型式 ,電子版
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