B2F2分子异构体结构的量子化学计算研究

采用abinitio方法对B₂F₂分子异构体的结构进行了计算研究,并与Al₂F₂分子进行了比较.结果表明,B₂F₂具有D_∞h对称性,³Σ_g电子态的直线型结构FBBF是B₂F₂分子的最稳定异构体,对文献的结果进行了修正.在UCCSD(T,full)/6－311+G(2df)水平下,F-B和B-B键长分别为0.12942和0.14820nm,振动频率出现在1860.00和1320.62cm^-1处.在UQCISD(T,full)/6－311+G(2df)//UMP2(full)/6－311+G(d)+ZPVE水平下,³Σ_g态的线性FBBF分子的垂直电离势为848.58kJ/mol,而由³Σ_g电子态的BF二聚为³Σ_g态的线性FBBF分子的焓变为59.86kJ/mol,此二聚化反应是放热反应,说明二聚化过程在能量上是有利的.     

NC2S+离子的结构和稳定性的理论研究

在密度泛函和从头算理论水平下计算了单重态的NC2S+离子的结构、能量、光谱以及稳定性. 在B3LYP/6-311G(d)水平下, 得到8个异构体, 它们由15个过渡态相连接. 在CCSD(T)/6-311+G(2df)//QCISD/6-311G(d)+ZPVE水平下, 得到能量最低的异构体是直线型的具有1Σ电子态的NCCS+(1)(0.0 kJ/mol), 其次是直线型的异构体CNCS+(2)(54.8 kJ/mol). 两个低能量的异构体1和2及另外一个高能量的直线型异构体CCNS+(3)(323.8 kJ/mol)都具有相当大的动力学稳定性, 这三个异构体在具备一定条件的实验室和星际条件下是可以进行观测的. 分析了这3个异构体的成键性质.     

HSCCS自由基势能面的理论研究

在CCSD(T)/6-311G(d,f)//MP2/6-311G(d,f) ZPE水平下,计算得到含有8个异构体和11个过渡态的HSCCS自由基体系势能面,讨论了异构体的结构与稳定性及异构体之间的异构化过程.结果表明异构体m1的能量最低,除m1以外,异构体m2和m3的能量也比较低,在MP2水平上,过渡态TS1的能量比异构体m2仅高3.9kJ/mol,而在CCSD(T)水平上,TS1的能量比m2低14.6 kJ/mol,这说明异构体m2可以迅速转化为能量更低的m1.异构体m3的能量比异构体m1高49.99 kJ/mol,可以推断,在合适的实验条件下可以观测到异构体m1.     

三重态SiCP2异构体的结构和稳定性的理论研究

采用DFT,QCISD和CCSD(T)等理论计算方法对三重态SiCP2异构体的结构和稳定性进行了理论研究.在B3LYP/6-311G(d)水平下,共计算得到由17个过渡态相连接的15个异构体.在CCSD(T)/6-311 +G(2df)//QCISD/6-311G(d)水平下,考虑重点振动能相对能量最低的三元环状异构体P-cCSiP 8(0.0 kJ/mol)及四元环状结构的cPCSiP 4具有相当大的动力学稳定性,在一定的实验室和星际条件下可能被检测到.另外,对它们的成键性质也进行了分析.     

高级量子化学从头计算法研究N2和H2O分子间相互作用

在MP2/6-311++G(3d,3p)电子相关校正水平上,对N₂和H₂O分子间可能存在的氢键复合物进行全自由度能量梯度优化,发现了一个接近于直线的弱氢键总能量极小结构(1),进一步在高级电子相关校正的MP4SDTQ和CCSD(T)水平,用6-311++G(3d,3p)基组加上(3s3p2d1f)键函数,用MP4和CCSD(T)计算的结构1的结合能分别为-5.061kJ/mol和-4.715kJ/mol.     

乙硼烷离子和自由基结构的量子化学研究

用B₃LYP/6-311G(d,p)密度泛函方法对B₂H₅⁺阳离子和B₂H₅^·自由基的几何异构体的空间构型进行了优化,并在此基础上用QCISD(T)/6-311++G(3df,2p)偶合簇法进行了单点能计算和零点能校正.结果表明,B₂H₅⁺单态有2种稳定的几何构型(D_3h,C₁),其中C₁构型是新发现的.B₂H₅⁺三重态阳离子除已知C_s构型外,又发现两种稳定构型(C₁).对于B₂H₅^·自由基体系,共有4种异构体(包括两种新发现的构型C_s),其中,具有单桥结构的C_2v最稳定.用二级多体微扰理论和密度泛函方法对前人所认为稳定的B₂H₅⁺单态的C_2v构型进行了全优化,结果发现该构型始终具有一个虚频,不是稳定构型.对B₂H₅^-阴离子体系的单态和三重态进行的全优化,理论上得出单态时具有C_2v和C_s两种稳定构型,而三重态只有C_2v一种稳定构型.     

HAsS2异构体结构与稳定性

在MP2/6-311++G(d,p)和QCISD(t)/6-311++G(3df,2p)(单点)水平下计算得到9个异构体和10个过渡态的HAsS₂体系势能面.异构体cis-HSAsS(E1)的能量最低,其次是trans-HSAsS(E2)、具有AsSS三元环的立体HAs(S)S(C_{s,E3)和HAs(S)S(C2v,E4)结构的异构体,能量分别比cis-HSAsS高1.46,60.78和93.63kJ/mol.根据体系的势能面,异构体E1,E2,E3和E4具有一定的动力学稳定性.AsH和S2第一步反应产物将会异构化为具有较高动力学稳定性的异构体E3,而SH和AsS第一步反应产物将会异构化为E1.计算结果与HNO2,HNS2,HPO2,HPS2和HAsO2等价电子相同的分子的势能面进行了比较.}     

Al2F2分子结构与稳定性的ab initio计算研究

用abinitio方法在UMP2/6-311G(d)水平下计算了Al2F2分子可能的异构体构型和AlF二聚化成Al2F2分子的反应能。UMP2/6-311G(d)和UQCISD(T)/6-311+G(3df)//UMP2/6-311G(d)水平下的能量值均说明具有D2h对称性、1^Ag电子态的异构是Al2F2分子的最稳定构型,其Al-F键长为0.19074nm,键角Al-F-Al和F-Al-F分别为104.62°和75.38°,以及两个强振动,441.27cm^-1和401.93cm^-1,均与实验结果相符合。电子结构分析表明,具有D2h对称性的异构体的活性中心在2个Al原子上,在形成衍生物时是主要的反应加成位置。在UMP2/6-311G(d)和UQCISD(T)6-311+G(3df)//UMP2/6-311G(d)水平下得到了AlF二聚化能量分别为-75.01kJ/mol和-66.07kJ/mol,与文献估计算基本一致,说明AlF二聚化反应能量上是有利的。     

HPS2异构体结构与相对稳定性

在MP2/6-311++G(d,p)和QCISD(t)/6-311++G(3df,2p)(单点)水平下计算得到了包括9个异构体和15个过渡态的HPS2势能面.其中,异构体trans-HSPS(E1)的能量最低, 其次是cis-HSPS(E2)和HPS(S)(C2_V,E3),能量分别比trans-HSPS(E1)高3.43和14.17 kJ/mol.计算结果表明,异构体E1,E2,E3和立体的三元环结构的异构体HP(S)S(C_S,E4), 及与E4共存的trans-HPSS(E5)和cis-HPSS(E6)具有一定的稳定性.在QCISD(t)/6-311++G(3df,2p)//MP2/6-311++G(d,p)并包含零点能水平下,PH和S₂反应生成的E6和E5分别越过65.75和71.73 kJ/mol的势垒就可以异构化为具有较高动力学稳定性的产物E4, 计算结果对实验认定的产物是cis-HPSS(E6)的结论进行了修正.     

气相离子-分子反应B2H3-+CS2——B2H3S-+CS的理论研究

用密度泛函方法B3LYP/6-311++G(d,p)和高级电子相关的偶合簇法CCSD(T)/6-311++G(d,p)研究了气相离子-分子反应B₂H₃^-+CS₂B₂H₃S^-+CS的机理.结果表明,B₂H₃最可能进攻CS₂中碳原子形成三元环中间体,随后通过氢迁移和最终消除CS的反应步骤形成硫原子转移产物H₃BBS^-+CS,反应大量放热且不需要活化能.B₂H₃直接对CS₂中硫原子进攻夺取硫原子的反应方式存在一定能垒阻碍.计算结果有助于深入了解B₂H₃,B₃H-6和B₄H₇^-等缺电子硼氢负离子的反应行为.     

B2N2分子结构与性质的理论研究

錋氮(BN)及其团簇分子在材料科学中的重要性而引起广泛关注,BN纳米管、纳米线及其团簇已被合成并在对其结构与性质进行了理论研究[1-7]。BN二聚物包括线性、正方形和棱形BN-BN结构,在MP2水平上的理论预测单重态稳定性为菱形(D2h)大于正方形(D2h)大于线性(C∞v)[8],但作者未对优     

Theoretical Studies on Structures and Stabilities of C4H2+ Isomers

The structures, energies, stabilities and spectroscopies of doublet C₄H₂⁺ cations were explored at the DFT/B3LYP/6-311G(d,p), CCSD(T)/6-311+G(2df,2pd)(single-point), and G3B3 levels. Ten minimum isomers including the chainlike, three-member-ring, and four-member-ring structures are interconverted by means of 15 interconversion transition states. The potential energy surface was investigated. At the CCSD(T)/6-311+G(2df,2pd) and G3B3 levels, the global minimum isomer was found to be a linear HCCCCH. The structures of the stable isomer and its relevant transition state are further optimized at the QCISD/6-311G(d,p) level. The bonding nature and structure of isomer HCCCCH were analyzed.     

Ti,Na与O2反应机理的理论研究

基于MP2/6-311+G(d)水平, 分别对过渡金属Ti和碱金属Na与O2的反应机理进行了研究. 比较了Ti和Na分别以垂直O—O键和沿着O—O键的方向逼近O2, 以及中性体系Ti/Na+O2和带1个负电荷的体系(Ti/Na+O2)-的情况. 详细分析了不同反应路径的结合能和电荷变化的曲线, 预测了最佳反应方式. 结果表明, 垂直接近方式要比水平接近方式更具有优势; 体系带一个负电荷(Ti/Na+O2)-有利于金属与O2的结合. 同时, 计算结果表明在Ti+O2和(Ti+O2)-体系中Ti容易与单态的O2结合; 在中性体系中Na也容易与单态O2结合, 而在(Na+O2)-体系中Na与三态O2的结合更稳定. 在CCSD(T)/6-311++G(3df)//MP2/6-311+G(d)水平下, 计算了Ti+O2和(Ti+O2)-的反应势能面.     

Ab Initio Study on the Potential Energy Surfaces of B4 Cluster

The singlet and triplet potential energy surfaces (PES) for the isomerization and dissociation reactions of B₄ isomers have been investigated using ab initio methods. Ten B4 isomers have been identified and of these 10 species, 4 have not been reported previously. The singlet rhombic structure ¹1 is found to be the most stable on the B₄ surface, in agreement with the results of previous reports. Several isomerization and dissociation pathways have been found. On the singlet PES, the linear ¹3b can rearrange to rhombus ¹1 directly, while ¹3c rearranges to ¹1 through two‐step reactions involving a cyclic intermediate. On the triplet PES, the capped triangle structure ³2 undergoes ring opening to the linear isomer ³3b with a barrier of 34.8 kcal/mol and 44.9 kcal/mol, and the latter undergoes ring closure to the square structure ³1 with a barrier of 30.4 kcal/mol and 33.0 kcal/mol at the MP4/6–311+G(3df)//MP2/6–311G(d) and CCSD/aug‐cc‐pVTZ//MP2/6–311G(d) levels of theory, respectively. The direct decomposition of singlet B₄ yielding to B₃+B is shown to have a large endothermicity of 87.3 kcal/mol (CCSD), and that producing 2B₂ to have activation energy of 133.4 kcal/mol (CCSD).     

丁烯和丁烷自由基阳离子的分子结构和超精细结构的 理论研究

用密度函数理论B3LYP方法和6-31G(d,p),6-311G(d,p)及6-311+G(d,p)基组，分别对1-C4H^+~8,2-C4H^+~8和C4H^+~10进行了构型优化和频率分析计算，预言1-C4H^+~8具有非平面构型，与以往报道的从头算和密度函数理论计算结果不同。在各自由基阳离子的B3LYP构型上，进行了B3LYP、MP2及MRSDCI方法的超精细偶合常数计算，得到了比以往更好的结果，特别是MP2/B3LYP计算值是至今与实验值符合得最好的理论计算结果。     

FC(O)O自由基与NO2反应的量子化学研究

用量子化学DFT, MP2, G3和G3MP2方法对FC(O)O自由基与NO₂的反应机理进行了理论研究. 优化了反应势能面上各驻点的几何结构, 通过内禀反应坐标(IRC)计算和振动分析, 确认了反应中的过渡态, 并用过渡态理论(TST)计算了相关反应的速率常数.     

Au+(1S, 3D)与N2O(1Σ+)反应机理的理论研究

采用密度泛函B3LYP方法, O和N用6-311+G*基组, Au+用赝势基组(8s7p6d)/[6s5p3d], 研究了Au+(1S, 3D)离子和N2O(1Σ+)分子的反应机理. 报道了在基态单重态和激发三重态势能面上各反应物、中间体和过渡态的构型特征及能量. 结果表明, 两个主反应通道Au+(1S)+ N2O(1Σ+)→1NA-Complex-1→1NA-TS1→1NA-Complex-2→1NA-Crossing→[3OAuNN]+和Au+(1S)+ N2O(1Σ+)→1NB-Complex→1NB-Crossing→[AuNN(1Σ+)]++O(3P)都需经过反应交叉势能面, 出现“系间窜越”. 用内禀坐标单点计算垂直激发态的方法确定了势能面交叉点, 并用含时密度泛函TD-B3LYP方法进一步探讨了自旋翻转机理.     

Ionized state of hydroperoxy radical-water hydrogen-bonded complex: (HO2-H2O)+

Ab initio molecular orbital calculations have been employed to characterize the structure and bonding of the (HO2-H2O)+ radical cation system. Geometry optimization of this system was carried out using unrestricted density functional theory in conjunction with the BHHLYP functional and 6-311++G(2df,2p) as well as 6-311++G(3df,3p) basis sets, the second-order M?ller-Plesset perturbation (MP2) method with the 6-311++G(3df,3p) basis set, and the couple cluster (CCSD) method with the aug-cc-pVTZ basis set. The effect of spin multiplicity on the stability of the (HO2-H2O)+ system has been studied and also compared with that of oxygen. The calculated results suggest a proton-transferred hydrogen bond between HO2 and H2O in H3O3+ wherein a proton is partially transferred to H2O producing the O2...H3O+ structure. The basis set superposition error and zero-point energy corrected results indicate that the H3O3+ system is energetically more stable in the triplet state; however, the singlet state of H3O3+ is more stable with respect to its dissociation into H3O+ and singlet O2. Since the resulting proton-transferred hydrogen-bonded complex (O2...H3O+) consists of weakly bound molecular oxygen, it might have important implications in various chemical processes and aquatic life systems.     

Ceometries,Energetics and Spectroscopic Properties of Oxygen Clusters Oxy (x=2～6, y=-2～2)

The geometries, energetics and spectroscopic properties of oxygen clusters, Oxy(x=2~6, y=-2~2), were investigated at the B3LYP/6-311G (d, p) level. The CASSCF calculations were carried out for the ground and excited states of3O2and2O2+. The total energy is3O2(3Σg-)<2O2-(2Πgi)<1O2(1Δg)<1O2-2(1Σg+)<2O2+(2Πg)<1O2+2(1Σg+). The relative energy of the active doublet anion of oxygen molecule,2O2-(2Πgi), is only 28 kJ/mol higher than the triplet neutral oxygen molecule,3O2(3Σg-). The calculated O-O vibrational frequencies all are in good agreement with the experimental values. They are 1577 (1580), 1139 (1090), 1563 (1484), 627 (615~545) and 1993 (1905) cm-1, where the O-O vibrational frequency values in parentheses are experimental values, for3O2(3Σg-),2O2-(2Πgi),1O2(1Δg),1O2-2(1Σg+) and2O2+(2Πg), respectively. Moreover, the O-O vibrational frequency of1O2+2(1Σg+) was computed as 2368 cm-1which has not been reported before at both experimental and theoretical levels. Both bent and linear geometries of O3were studied. The bent-types of O3are more favorable than the linear-type in energy. Three types of structure for oxygen trimers are calculated at the B3LYP/6-311G (d, p) level. They are the structure-I with an obtuse angle of O-O-O,the structure-II with an acute angle of O-O-O, and the structure-III of linear type. For a bent-type structure of O3species (structure-I), the total enegy is2O3-(2B1)<1O3(1A1)<3O3(3B2)<1O3-2(1A1)<2O3+(2A1). The optimization of geometry at B3LYP/6-311G (d, p) level indicated that the species of2O3-(2B1) with 1.3573 of O-O bond length and 115.6584o of O-O-O bond anger is the ground state of O3. The total energy of O4species and their ions is2O4-(Cs,2A′, bend-type)<2O4-(C2v,2A2,face-centered triangle-type)<2O4-(D∞h,2Σg, linear-type)<1O4(Cs,1A′, bend-type)<1O4(D∞h,1Σg, linear-type)<1O4(D4h,1A1g, square-type)<1O4(C2v,1A1, face-centered triangle-type)<2O4-(D4h,1A1g, square-type)<2O4+(D∞h,2Σg, linear-type)<2O4+(Cs,1A′, bend-type). The species with the lowest relative energy is an anion,2O4-(Cs,2A′, bendtype), with chair form geometry and characteristic vibronic frequencies of 1179 and 1349 cm-1. The relative energy of1O5(C2v,1A1) with coplanar-triangle-bicone geometry is the lowest among the O5species and their ions, which may be a resonance structure with1O5(C2v,1A1) of A type. Their characteristic vibronic frequency is 1302 cm-1. The relative energy of the O6species and their ions with hexagon geometry is lower than one with linear geometry. Their infrared vi-bronic intensity may be weak and unobservable but the Raman vibronic intensity may be strong and observable based on their symmetry.