西北师范大学学报(自然科学版)
西北師範大學學報(自然科學版)
서북사범대학학보(자연과학판)
Journal of Northwest Normal University (Natural Science)
2015年
6期
63-70
,共8页
密度泛函理论(DFT)%最低能量交叉点(MECP)%自旋-轨道耦合(SOC)%转化频率(TOF)%反应机理
密度汎函理論(DFT)%最低能量交扠點(MECP)%自鏇-軌道耦閤(SOC)%轉化頻率(TOF)%反應機理
밀도범함이론(DFT)%최저능량교차점(MECP)%자선-궤도우합(SOC)%전화빈솔(TOF)%반응궤리
density functional theory (DFT )%minimum energy crossing point (MECP )%spin-orbit coupling(SOC)%turnover frequency(TOF)%reaction mechanism
为了说明两态反应会影响甚至决定整个反应的反应速率或选择性,运用密度泛函(DFT )B3lyp/6‐311+ G (3df ,2p)方法,对TiO催化CO2加氢生成甲酸反应的单、三重态各个驻点结构进行优化。发现在两个自旋态势能面之间有四处能量交叉点(CPs),由此找出最低能量交叉点(MECP),根据交叉点的构型计算自旋‐轨道耦合(SOC)常数,用Landau‐Zener非绝热跃迁公式计算出M ECP处的跃迁几率,发现四处最低能量交叉点都具有较强的自旋‐轨道耦合作用和较高的跃迁几率,且四个最低能量交叉点处电子的自旋翻转均发生在Ti原子不同的d轨道之间,确定了最低能量反应路径。用能量跨度模型计算了在298 K下TiO的转化频率(TOF)及整个过程的控制度(XTOF ),同时确定了整个反应过程中的决速态。
為瞭說明兩態反應會影響甚至決定整箇反應的反應速率或選擇性,運用密度汎函(DFT )B3lyp/6‐311+ G (3df ,2p)方法,對TiO催化CO2加氫生成甲痠反應的單、三重態各箇駐點結構進行優化。髮現在兩箇自鏇態勢能麵之間有四處能量交扠點(CPs),由此找齣最低能量交扠點(MECP),根據交扠點的構型計算自鏇‐軌道耦閤(SOC)常數,用Landau‐Zener非絕熱躍遷公式計算齣M ECP處的躍遷幾率,髮現四處最低能量交扠點都具有較彊的自鏇‐軌道耦閤作用和較高的躍遷幾率,且四箇最低能量交扠點處電子的自鏇翻轉均髮生在Ti原子不同的d軌道之間,確定瞭最低能量反應路徑。用能量跨度模型計算瞭在298 K下TiO的轉化頻率(TOF)及整箇過程的控製度(XTOF ),同時確定瞭整箇反應過程中的決速態。
위료설명량태반응회영향심지결정정개반응적반응속솔혹선택성,운용밀도범함(DFT )B3lyp/6‐311+ G (3df ,2p)방법,대TiO최화CO2가경생성갑산반응적단、삼중태각개주점결구진행우화。발현재량개자선태세능면지간유사처능량교차점(CPs),유차조출최저능량교차점(MECP),근거교차점적구형계산자선‐궤도우합(SOC)상수,용Landau‐Zener비절열약천공식계산출M ECP처적약천궤솔,발현사처최저능량교차점도구유교강적자선‐궤도우합작용화교고적약천궤솔,차사개최저능량교차점처전자적자선번전균발생재Ti원자불동적d궤도지간,학정료최저능량반응로경。용능량과도모형계산료재298 K하TiO적전화빈솔(TOF)급정개과정적공제도(XTOF ),동시학정료정개반응과정중적결속태。
To illustrate the two state reaction will influence and even determine the reaction rate of the whole or selectivity ,the density functional method(DFT) B3lyp/6‐311+ G(3df ,2p) is used to optimize CO2 hydrogenation to generate formate catalyzed by TiO of singlet and triplet stagnation point structure in the gas phase .Under the whole catalytic cycle ,there are four crossing points between singlet and triplet potential energy surfaces . T he possibilities of spin flip at M ECPs are discussed through spin‐orbit coupling calculations . T he electron transition probability are calculated by Landau‐Zener formula , 4 M ECPs has strong spin‐orbit coupling effect and higher transition probability , and all spin inversion is occurred in different d orbits of titanium . Finally , the lowest energy reaction path is ensured . The turnover frequency(TOF) and XTOF at 298 K have been obtained by citing the energetic span model proposed by Kozuch . T he fast mode in the process of reaction is determined .