期刊論文

標題 Ab Initio Study of the Reaction Mechanisms of NiO and NiS with H2
學年 90
學期 1
出版(發表)日期 2002/01/24
作品名稱 Ab Initio Study of the Reaction Mechanisms of NiO and NiS with H2
作品名稱(其他語言)
著者 黃德彥; Hwang, Der-yan; Mebel, Alexander M.
單位 淡江大學化學學系
出版者 Washington: American Chemical Society (ACS)
著錄名稱、卷期、頁數 Journal of physical chemistry A 106(3), pp.520-528
摘要 Singlet and triplet potential energy surfaces for the NiO + H2 → Ni + H2O and NiS + H2 → Ni + H2S reactions have been investigated by density functional calculations at the B3LYP/6-311+G(3df,2p)//B3LYP/6-31G** level as well as by ab initio CCSD(T), CASSCF, and MRCI calculations for some of the key species. The singlet−triplet intersystem crossing is shown to play a crucial role for both reactions. The reaction of nickel oxide with molecular hydrogen starts from the formation of a t-ONi−H2 complex bound by 3.7 kcal/mol relative to NiO(3Σ-) and H2. This is followed by an intersystem crossing (the spin−orbit coupling computed at a representative point CI1 of the singlet−triplet intersection is 86 cm-1) and the system proceeds via a barrier of 13.3 kcal/mol (transition state s-TS1) in singlet electronic state to form a HNiOH intermediate in singlet or triplet states. t-HNiOH, 9.1 kcal/mol more stable than s-HNiOH, lies 44.8 kcal/mol below the reactants. The HNiOH molecule rearranges to a triplet t-Ni−OH2 molecular complex via transition state s-TS2 on the singlet potential energy surface and via singlet−triplet transitions, whereas the spin−orbit coupling for a crossing point CI2 in the transition state vicinity is evaluated as 27 cm-1. On the last reaction step the complex bound by 3.8 kcal/mol dissociates to Ni(3F) + H2O without an exit barrier. For the reverse reaction, Ni(3F) + H2O → t-HNiOH, the barrier, which occurs at s-TS2 in singlet electronic state, is 12.1 and 4.9 kcal/mol at the B3LYP/6-311+G(3df,2p) and CCSD(T)/6-311+G(3df,2p) levels, respectively. The NiS + H2 reaction begins on the triplet potential energy surface and proceeds via a barrier [transition state t-TS1(S)] of 19.1 kcal/mol relative to NiS(3Σ-) + H2 to produce the global minimuma triplet HNiSH molecule, 18.2 kcal/mol below the reactants. This intermediate dissociates to the triplet Ni atom and H2S via s-TS2(S) and a s-Ni−SH2 complex involving singlet−triplet intersections. The Ni(3F) + H2S reaction is predicted to rapidly produce the HNiSH molecule, which, in turn, can dissociate to NiS + H2 overcoming a barrier of 13 kcal/mol with respect to the reactants. Since the highest barriers along the NiO + H2 → Ni + H2O and NiS + H2 → Ni + H2S reaction pathways are 13 and 19 kcal/mol, molecular hydrogen is expected to reduce nickel oxide and NiS to atomic nickel at elevated temperatures.
關鍵字
語言 英文
ISSN 1089-5639
期刊性質 國外
收錄於
產學合作
通訊作者
審稿制度
國別 美國
公開徵稿
出版型式 紙本