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采用密度泛函理论的UB3LYP方法,计算研究了气相中La+活化NH3的两态反应机理。为了理解由La+活化NH3过程中自旋翻转行为,对自旋态分别为单重态和三重态两个反应势能面进行了计算研究,其结果表明,La+活化NH3的过程是通过自旋态势能面交叉产生的自旋禁阻反应,单、三重态势能面最低能量交叉点(MECP)附近的系间窜越导致H向La+转移和脱H2反应能垒的降低。此外,运用自然键轨道(NBO)布居分析,研究了反应中各个物种的成键特性。所确定的最低能量反应路径为:3La++NH3→3IM1→MECP→1TS12→1IM2→1TS23→1IM3→1LaNH++H2。
The density functional theory UB3LYP method was used to study the two-state reaction mechanism of La + activation of NH3 in the gas phase. In order to understand the spin-flip behavior in the activation of NH3 by La +, we calculated the spin-state singlet and triplet reaction potential surfaces. The results show that the activation of NH3 by La + The spin-forbidden reaction produced by cross-coupling resulted in the decrease of energy barrier of H-transfer to La + and H2-removal reaction in the vicinity of the lowest energy cross point (MECP) of single and triplet potential energy surfaces. In addition, using the natural bond orbital (NBO) population analysis, the bonding characteristics of various species in the reaction were studied. The determined minimum energy reaction path is: 3La ++ NH3 → 3IM1 → MECP → 1TS12 → 1IM2 → 1TS23 → 1IM3 → 1LaNH ++ H2.