Structure and Electronic Properties of Single Walled Nanotubes from AlAs(111) Sheets: A DFT Study

通过卷曲立方AlAs(111)单层片(sheets)构造了一系列(n,0)和(n,m)一维单壁纳米管。用周期性密度泛函理论(DFT)计算并比较了; 不同类型AlAs纳米管在几何结构、能量及电子性质等方面的差别。计算结果表明锯齿型和椅型纳米管应变能均为负值,并随着管径变大而逐渐变小。然而,它们; 的带隙相当不同:椅型纳米管为间接带隙,随着管径的增大而带隙减小;锯齿型纳米管为直接带隙,管径为1.87 nm时存在着一个极大带隙值(2.11; eV)。这种不同主要源于锯齿型纳米管铝原子间3p轨道的耦合贡献。A series of AlAs nanotubes (NTs) can be formed by rolling up two dimensional periodic (111) single layer sheets, namely (n,0) and (n,m) nanotubes. Optimized parameters of the atomic arrangement, energy levels and electronic structure of corresponding nanotubes of different types were calculated and compared by the density functional theory (DFT) method. The calculated results showed that strain energies (E-s) are negative over most of the diameter range for the (n,0) and (n,m) series, indicating that these NTs are more stable than a planar AlAs(111) single layer. The strain energy gradually decreases with increasing diameter. The calculated electronic band structures and density of states profiles reveal that the indirect band gaps (E-g) of armchair AlAs nanotubes gradually decreases with increasing diameter, which is distinct behavior from the zigzag nanotubes. The zigzagAlAs nanotubes feature a direct Eg with a peak value (2.11 eV) for a tube of radius 1.87 nm. The origin of the differences in band gaps could be attributed to the p-p coupling interaction between Al 3p orbitals in the conduction band of the AlAs zigzag nanotube.国家自然科学基金（21573182）资助项

符合独立五元环规则的C100（417）Cl28形成机理的密度泛函理论研究

实验上捕获到C100（417）Cl28,但其形成机理仍不清楚。本文采用密度泛函理论（DFT）方法研究了生成C100（417）Cl28的反应机理,考虑了可能的经Stone-Wales（SW）转化、直接氯化和来自于骨架转变等反应路径。结果表明:C100（417）Cl28形成的最主要来源是通过C102（603）骨架转变,即经历氯化、C2失去和SW转变而来。该结果能很好解释实验结果,对富勒烯氯化物的合成提供了理论依据。国家自然科学基金(21573182)资助项目~

重师博物馆匾额文本的女性、等级与宗族社会解读

匾额是中国传统文化的重要载体和组成部分,其隐藏着包罗万象的信息,具有重要的历史、艺术、文学等多学科的研究价值。本文试图从历史学的角度,试图透视重庆师范大学博物馆所藏匾额1中所隐含着的历史信息,主要围绕匾额中的女性、匾额中的等级关系以及匾额中的家庭与宗族三个主题进行解读,进一步彰显匾额的作用和价值

活性碳上羧酸根锚定AuCl3催化乙炔氢氯化反应的理论研究

采用密度泛函B3LYP方法,运用分子模型对活性碳（AC）上羧酸根负载AuClx催化剂的活性结构、稳定性以及催化乙炔氢氯化反应机制进行了详细的理论探讨。结果表明,AuCl3催化剂可以被表面羧酸根单中心级分散锚定,形成AC-COOH-AuCl3表面活性中心,进而在氢氯化过程中与乙炔发生协同加成生成氯乙烯,同时形成具有螯合结构的表面活性中心AC-CO2>AuCl2,进而催化氢氯化反应遵循分步反应异步加成机制:乙炔活化吸附到Au（Ⅲ）中心,HCl异裂亲核加成到乙炔伴随羧酸根质子化,分子内质子迁移形成Au（Ⅲ）-氯乙烯d-π配键络合物,氯乙烯脱除恢复AC-CO2>AuCl2螯合结构。计算还表明,AC-COOH-AuCl3表面活性中心比Au2Cl6催化组分更不易被乙炔还原失活。国家自然科学基金(91545105,21273177

A Theoretical Study of the Mechanism for Allylic Ether Isomerization

采用MP2和密度泛函M06-2X方法,在6-31++g(d,P)基组水平上对烯丙基类不对称醚异构化反应机理进行了计算研究.揭示了其可能的反应途径,预测了互变异构吉布斯自由能,活化能等性质.计算结果表明,在没有金催化剂的条件下,尽管有醇溶剂时异构化活化能垒有所降低,异构化反应依然不容易进行.相反,存在金催化剂并且有醇溶剂情况下,烯丙基类不对称醚异构化反应活化自由能大大降低,仅为7.5 kCAl/MOl.通过比较有无醇溶剂和金催化剂对异构化的影响,揭示了金烯烃络合和醇分子参与反应以质子转移的异构化反应机理,很好解释了实验中观察的现象.计算结果还表明:醇分子不仅参与反应提供质子转移,它还能与醚竞争金催化剂络合,因此在高浓度醇条件下会抑制异构化反应进行.The reaction mechanism of allylic ether isomerization has been investigated by MP2 and DFT method(different functionals) with 6-31++G(d,p) basis set.The calculated results show that M06-2X method that designed to treat dispersion and hydrogen-bonded systems do better than traditional functional-B3LYP for the calculated energetic and structural properties of allylic ether isomerization.The optimal structures of allylic ether and transition states were located and the reaction Gibbs free energy barriers were predicted at the MP2 and M06-2X level.Furthermore, the possible reaction pathways and mechanisms were proposed to explain the origin of regioselectivity observed in experiment.The calculation results show that the isomerization reaction will not readily occur in the absence of catalysis by Au.The computed potential energy barrier is quite high, and things get better when alcohol molecules are introduced, resulting in the decrease of calculated activation free energy from 67.1 to 48.6 kcal/mol.However, the Au(I)-catalyzed addition of another molecule of alcohol to an allylic ether can occur readily.A protonated diether intermediate was stabilized by a hydrogen bond and the activation energies of allylic ether isomerization were dramatically decreased, only 7.5 kcal/mol.By contrast the isomerization effect under with and without alcohol, gold catalysis, the results indicate that the allylic ether isomerization involve cationic gold coordination and proton shift reaction process, which form the intermediate that allows the interconversion of the products.This reaction mechanism can successfully explain the observed regioselectivity for the thermodynamic product.Meanwhile, the results also show that the isomerization was completely inhibited with the excess alcohol due to competing gold coordination between alcohol and ether.The discovery of gold catalysts in allylic ether isomerization not only contributes to the development of catalysts from the usual transition metals to noble metals, but also shows the potential catalytic activities by switching the reaction conditions.国家自然科学基金(No.21273177); 西部之光计划资助~

A Tight-Binding Density Functional Theory Study on Single-Walled Nanotubes from Anatase TiO_ 2 (101) Sheets

通过卷曲二维锐钛矿(101)周期性单层片(SHEETS)构造了一系列不同手性((n,0), (0,M), (n,M))的一维单壁TIO2纳米管. 用周期性紧束缚密度泛函理论(dfTb)方法计算并比较了不同管径和手性的TIO2纳米管在几何结构、电子性质等方面的差别. 结果表明: 除了(6,0)管, 其余纳米管随着管径的增大, 应变能和能隙减小. 而在管径相同的情况下, 不同手性的(n,M)纳米管的应变能随着n/M的增加呈现先增大后减小的趋势, 能隙变化不大.A series of chiral anatase(101) nanotubes(NT),which we refer to as(n,0),(0,m),and(n,m),can be formed by rolling up two-dimensional periodic anatase TiO2(101) single layer sheets.Optimized parameters of the atomic and electronic structures of these nanotubes have been calculated using a tight-binding density functional theory method(DFTB).Their band gaps(Eg) and strain energies(Es) have been analyzed as functions of NT diameter.Except for(6,0),the strain energy and the band gap of all the nanotubes of various chirality decrease as the diameter increases.We also find that the strain energy increases first and then decreases rather than varying monotonically with almost constant band gap when n/m ranges from zero to infinitely large.国家自然科学基金(20873107);国家重点基础研究发展规划项目(973)(2011CB808504)资助---

Ti2C80 is more likely a titanium carbide endohedral metallofullerene (Ti2C2)@C-78

We show by means of density functional calculations that the previously synthesized metallofullerene Ti2C80 does not take the form of Ti-2@C-80, but is a titanium carbide endohedral metallofullerene, Ti2C2@C-78, that has a C-78(6-)(D-3h) cage which follows faithfully the stable closed-shell electronic rule

Alternative Formation Mechanism of C_(50)Cl_(10) Fullerene Chloride Based on Density Functional Theory Calculations

过去广泛接受#271C50Cl10是由#271C50空笼直接氯化得到.我们通过研究拓扑结构弄清了C50富勒烯之间的相互关系.利用密度泛函理论(dfT)计算从最稳定C50富勒烯#270C50出发,通过氯化和STOnE-WAlES(SW)转变获得#271C50Cl10.结果表明:氯化后最终产物是热力学最有利的,并且在有氯存在下,SW转变的活化能垒会降低.这些结果可以解释目前的相关实验事实,暗示了#270C50空笼先氯化得到不同#270C50氯化物,再进行两次SW旋转的路径,由于活化能垒更低因而是一条更为可行的路线.#271C50Cl10is widely postulated to be a direct chlorination product of cage#271C50.We suggest an alternative formation mechanism of#271C50Cl10, based on the topological relationship of these C50 fullerenes.Density functional theory(DFT) calculations of the proposed cage transformation pathway in the chlorination of C50 were performed.The proposed pathway is stimulated by chlorination-promoted fullerene cage transformation, with a low activation barrier.DFT calculations of the Stone-Wales(SW) transformation pathways revealed that the thermodynamically favored rearrangement of other C50 chlorofullerene into#271C50Cl10requires a lower activation energy than that of the pristine carbon cage.This suggested that it is a more effective pathway of chlorinating C50to#271C50Cl10.国家自然科学基金(21273177); 国家重点基础研究发展规划项目(973)(2011CB808504)资助~

正、负和中性TiP_(10)团簇结构与电子性质的密度泛函研究

采用密度泛函理论的B3LYP方法研究了正、负和中性TiP10团簇的几何构型和电子结构.计算结果表明,中性TiP10团簇的基态构型为金属夹心结构,正、负离子团簇同样具有该基态稳定结构.通过对基态稳定结构的分子轨道分析表明,δ键对形成夹心结构起到重要作用.理论计算得到的中性TiP10团簇的垂直和绝热电离能分别为7.84和7.68eV,垂直和绝热电子亲和势分别为3.18和3.35eV

过渡金属氧化物(M_2O_5)_(m=1,2)~+(M=V,Nb,Ta)与C_2H_4气相反应机理的密度泛函研究

采用密度泛函理论研究了过渡金属钒族氧化物阳离子团簇(M2O5)m+=1,2(M=V,Nb,Ta)与C2H4气相反应机理.反应为(M2O5)m++C2H4→(M2O5)m-1M2O4++C2H4O,反应物先化合生成C—O键相连的化合物,经过过渡态后M—O键断裂,从而发生氧原子转移到碳氢化合物上的反应.对于V2O5+与C2H4的反应,存在经顺式和反式两种过渡态结构路径,从能量上看,经反式过渡态结构的路径更有利.计算结果表明,发生反应时C2H4与钒氧化物阳离子反应大量放热,而与铌、钽氧化物阳离子反应却放热较少甚至不放热,这与实验结果一致.钒、铌、钽氧化物阳离子团簇发生氧转移反应活性不同的原因是金属-氧键的强弱不同所致