Density Functional Theory Study of HCN Adsorption on Small Gold Clusters

A theoretical study was carried out on the adsorption of hydrocyanic acid on small Aun （n ≤ 7） clusters using density functional methods. For HCN adsorption on gold clusters, no dependence was found with respect to the even-odd alternation in relation to the number of gold atoms in the cluster. The HCN molecule is adsorbed at simple adsorption sites （1-fold coordination）, perpendicular to the adsorption site. The largest adsorption energy is only about 74.61 kJ·mol^-1, which indicates that the HCN molecule does not decompose and the C-N bond retains triple bond, and that the C-H and C-N stretching frequencies are only weakly perturbed. The adsorbed C-N and C-H stretching frequencies are blue- and red-shifted compared with the values of free HCN, respectively.     

Theory Study of the Adsorption of Hydrocyanic Acid onto Small Silver Clusters

Density functional theory calculations have been performed to study the interaction of small silver clusters, Ag2 ~Ag9, with HCN. The adsorption of HCN on-top site of the silver cluster, among various possible sites, is energetically preferred. The adsorption energies of HCN on the silver clusters reach a local maximum at n = 4, which is only about 0.450 eV, indicating that the adsorbed HCN molecule is weakly perturbed. The adsorbed C–N and C–H stretching frequencies are blue- and red-shifted compared with the values of free HCN, respectively.     

O与O2在Au团簇上吸附的密度泛函理论研究

采用基于密度泛函理论(DFT)的Dmol³程序系统研究了O原子与O₂在 Au₁₉与Au₂₀团簇上的吸附反应行为. 结果表明: O在Au₁₉团簇顶端洞位上的吸附较Au₂₀强; 在侧桥位吸附强度相近. O与O₂在带负电Au团簇上吸附较强, 在正电团簇吸附较弱. 从O―O键长看, 当金团簇带负电时, O―O键长较长, 中性团簇次之, 正电团簇中O―O键长较短, 因而O₂活化程度依次减弱. 电荷布居分析表明, Au团簇带负电时, O与O₂得电子数较中性团簇多, 而团簇带正电时, 得电子数较少. 差分电荷密度(CDD)表明, O₂与Au团簇作用时, 金团簇失电子, O₂的π^*轨道得电子, 使O―O键活化. O₂在Au₁₉^-团簇上解离反应活化能为1.33 eV, 较中性团簇低0.53 eV; 而在Au₁₉⁺上活化能为2.27 eV, 较中性团簇高0.41 eV, 这与O₂在不同电性Au₁₉团簇O―O键活化规律相一致.     

Sin/Si-n(n=2-6)的结构和电子亲合能的密度泛函理论研究

选用四种不同的密度泛函理论方法(B3LYP,BLYP,BP86,B3P86),在全电子的双ζ加极化加弥散函数基组(DZP++)下,研究Sin/Si-n (n=2 -6 )体系的结构和电子亲合能.预测Si2 /Si-2 ,Si3 /Si-3 ,Si4 /Si-4 ,Si5 /Si-5 和Si6 /Si-6 的基态结构分别为C∞h(3Σ-g ) /C∞h(2Σ+g ),D3h(3A′2 ) /C2υ(2A1 ),D2h(1Ag) /D2h(2B2g),D3h(1A′1 ) /D3h(2A″2 )和C2υ(1A1 ) /D4h(2A2u).在电子亲合能方面,B3LYP方法预测的电子亲合能是最可靠的.预测Si2,Si3,Si4,Si5和Si6的电子亲合能分别为 2. 05, 2. 34, 2. 16, 2. 48和 2. 13eV.     

Density Functional Theory Study of the Adsorption of C2H2 on the Cu/Pt(111) Bimetallic Surfaces

We applied periodic density-functional theory to investigate the adsorption of C2H2 on the Cu/Pt bimetallic and monometallic surfaces, including Cu-Pt-Pt and Pt-Cu-Pt representing the monolayer Cu on the Pt surface and subsurface Cu in the Pt surface, respectively. For the Pt(111) and Pt-Cu-Pt surfaces, C2H2 is preferentially a 3-fold "parallel-bridge" configuration, and a "μ-bridge" structure exists above the Cu(111) and Cu-Pt-Pt surfaces. The adsorption energy of C2H2 on these surfaces decreases in the order Pt(111) > Cu-Pt-Pt > Pt-Cu-Pt > Cu(111). The analysis of density of states, charge, and vibrational frequencies showed obviously weakening of the adsorbed C-C bond and high sp2 character on the carbon atom. Furthermore, when the top-layer compositions are equal, the nearer the EF d-band center is, the larger the C2H2 adsorption energy will be.     

槲皮素抗氧化活性的密度泛函理论研究

采用杂化密度泛函理论(DFT)方法, 预测了黄酮类化合物槲皮素分子的几何结构、电子结构和脱氢解离焓, 分析了这些性质与分子活性位的关系, 探讨了槲皮素分子的抗氧化活性, 即与活性氧自由基•OH, •OOH和 的反应机理. 在B3LYP/6-31＋G(d)水平下, 计算得到的槲皮素分子脱氢自由基的相对稳定性、脱氢解离焓和氢提取过程的活化能都表明, 槲皮素中的4 -羟基活性最高, 最有可能参与自由基的清除. 4 -羟基位的这种反应活性主要来源于相邻羟基之间的弱氢键相互作用. 深入研究槲皮素分子的抗氧化机理, 有助于更合理地设计和合成新的抗氧化剂.     

甲硫醇在Cu(111)表面的解离吸附: 密度泛函理论研究

采用基于密度泛函理论的第一性原理方法和平板模型研究了CH₃SH分子在Cu(111)表面的吸附反应.系统地计算了S原子在不同位置以不同方式吸附的一系列构型, 第一次得到未解离的CH₃SH分子在Cu(111)表面顶位上的稳定吸附构型,该构型吸附属于弱的化学吸附, 吸附能为0.39 eV. 计算同时发现在热力学上解离结构比未解离结构更加稳定. 解离的CH₃S吸附在桥位和中空位之间, 吸附能为0.75-0.77 eV. 计算分析了未解离吸附到解离吸附的两条反应路径, 最小能量路径的能垒为0.57 eV. 计算结果还表明S―H键断裂后的H原子并不是以H₂分子的形式从表面解吸附而是以与表面成键的形式存在. 通过比较S原子在独立的CH₃SH分子和吸附状态下的局域态密度, 发现S―H键断裂后S原子和表面的键合强于未断裂时S原子和表面的键合.     

Au(111)面甲烷硫醇吸附的密度泛函理论研究

采用基于密度泛函理论的第一性原理方法和平板模型研究了CH₃SH分子在Au(111)表面的吸附构型和电子结构. 系统地计算了S原子在不同位置以不同方式吸附的系列构型, 计算结果表明, CH₃SH分子倾向于吸附在top位上, S-C键相对于Au表面法线的夹角为62°～78°|而S-H键断裂后CH₃S_H则倾向于吸附在bri-fcc位上, S-C键相对于Au(111)表面法线的夹角为49°～57°. 比较分析CH₃SH分子和CH₃S_H的吸附, 发现CH₃SH分子倾向于不解离吸附, 表面温度的提升和缺陷的出现可能促使S-H键的断裂. 通过比较S原子在独立的CH₃SH分子和吸附状态下的局域态密度, 发现S-H键断裂后S原子和表面的键合强于S-H键未断裂时S原子和表面的键合. 扫描隧道显微镜(STM)图像模拟显示了CH₃SH和CH₃S_H在Au(111)表面吸附的3个典型的STM图像.     

水分子在MoO3原子簇模型表面吸附的密度泛函研究

利用密度泛函理论(DFT)的B3LYP方法,在LANL2DZ基组上,计算了水分子吸附前后MoO3原子簇模型物的优化几何构型和电子结构,并进行了二级Mφller-Plesset微扰(MP2)相关能计算.结果表明,当水分子吸附于模型分子后,由于占据了MO5+空位,从原来留有空位的MoO5H4模型转变为MoO5H4·H2O模型的正八面体构型,水分子的氧通过占据在π键轨道中的电子向中心原子Mo的d轨道配位而被吸附,且水分子在模型物质表面呈吸附状态后,体系最稳定,能量最小,吸附过程不必翻越能垒,该过程放热91.39kJ/mol(MP2相关能校正),研究结果对催化剂的使用、失活和再生有较好的指导意义.     

密度泛函理论研究十二烷硫醇在Au(111)面上的吸附

采用第一性原理方法研究了十二烷硫醇(C₁₂H₂₅SH)分子在Au(111)面上未解离和解离吸附的结构、能量和吸附性质,在此基础上分析判断长链硫醇分子在Au(111)面吸附时S―H键的解离, 以及分子链长度对吸附结构和能量的影响. 计算了S原子在不同位置以不同方式吸附的系列构型, 结果表明在S―H键解离前和解离后,均存在两种可能的表面结构, 直立吸附构型和平铺吸附构型; 未解离的C₁₂H₂₅SH分子倾向于吸附在top位, 吸附能为0.35-0.38 eV; H原子解离后C₁₂H₂₅S基团倾向于吸附在bri-fcc位, 吸附能量为2.01-2.09 eV. 比较分析未解离吸附和解离吸附, 发现C₁₂H₂₅SH分子未解离吸附相较于解离吸附要稳定, 未解离吸附属于弱化学吸附.局域电子态密度和差分电荷密度分析进一步验证了S―H解离后S原子与表面之间成键的数目增加, 而且键合更强. 同时我们发现长链硫醇的吸附能量较短链硫醇的吸附能量略大, S原子与表面Au原子之间的距离略小.     

Theoretical Study on the Optical Properties for 2,7- and 3,6-Linked Carbazole Trimers by Time-dependent Density Functional Theory

Electronic properties, such as HOMO and LUMO energies, band gaps, ionization potential (IP) and electron affinity (EA) of 2,7- and 3,6-linked carbazole trimers, two conjugated oligomers with different linkages of carbazole, were studied by the density functional theory with Becke-Lee-Young-Parr composite exchange correlation functional (B3LYP). The absorption spectra of these compounds were also investigated by time-dependent density functional theory (TD-DFT) with 6-31G* basis set. The calculated results indicated that the HOMO and LUMO of the 2,7- and 3,6-linked carbazole trimers are both slightly destabilized on going from methyl substitution to sec-butyl substitution. Both IP and EA exhibit their good hole-transporting but poor electron- accepting ability. The presence of alkyl groups on the nitrogen atoms does not affect the intra-chain electronic delocalization along the molecular frame. Thus no significant effect on the band gap and absorption spectra of compounds has been found.     

密度泛函理论研究聚烯烃催化剂取代基电子效应与催化活性的关系

 采用密度泛函 BP/DNP 优化了五组 (每组化合物具有相同的框架结构和不同电子效应的取代基) 共 18 个最受关注的烯烃配位聚合催化剂, 分别计算了每个化合物中心金属上的 Hirshfeld、Mulliken 和 QEq 电荷, 中心金属的 Fukui 指数以及化合物的 HOMO 和 LUMO 能量值, 然后将这些结构参数和配合物催化乙烯聚合的活性相关联. 结果发现, 中心金属的 QEq 电荷能正确反映取代基的电子效应, 且与化合物的 HOMO 以及 LUMO 能量值与催化活性之间有良好的相关性, 可用来预测催化剂活性; 而 Hirshfeld 和 Mulliken 电荷不能正确反映取代基的电子效应, 不适合计算这些化合物的中心金属电荷. 中心金属的 Fukui 指数受取代基电子效应影响较小, 和催化剂活性之间的相关性不明显.     

固—液界面阴离子集团构型的密度泛函理论研究

通过键合不同数量的H2PO4^-离子构造了H4P2O8^2-和H4P4O16^8-两种阴离子集 团。利用密度泛函理论对它们的构型进行优化并计算其振动频率和喇曼散射效率。 测量了固—液界面边界层的喇曼光谱并与理论计算结果进行对比分析，进一步研究 了阴离子集团的结构、聚合及脱水等过程。实验和理论研究均表明阴离子二聚体是 KDP晶体的生长基元，他们在固液界面将进一步形成多聚体分子集团，而离子集团 的脱水过程则发生在距KDP晶体表面约50μm的固—液界面边界层中。随着生长层向 界面的推进，这些分子集团将变得越来越有序。本文的研究结果对确定晶体生长界 面动力学过程、发展和完善晶体生长理论有重要意义。     

A Density Functional Theory Study on the Adsorption of CN on Ni(111) Surface

1 INTRODUCTION Cyanide, CN, is an important free-radical mole-cule of one carbon chemistry, organic chemistry, free-radical chemistry and cosmochemistry. And the im-portant industrial processes, such as the Andrussovreaction, depend on the reactivity of CN bond[1]. Thechemistry of cyanide is also important in the surfacechemistry of a number of C- and N-containing sys-tems[1, . During the past decade, the adsorption of 2]CN and CN-containing molecules on transition metalsurfa…     

Density Functional Theory Study on the Structural and Electronic Properties of Ge（SiO_2）_n Clusters

The geometry,stability,binding energy and electronic properties of(SiO2)n and Ge(SiO2)n clusters(n = 7) have been investigated by Density functional theory(DFT).The results show that the lowest energy structures of Ge(SiO2)n are obtained by adding one Ge on the end site of the O atom or the Si near end site of the O atom in(SiO2)n.The chemical activation of Ge-(SiO2)n is improved compared with(SiO2)n.The calculated second-order difference of energies and fragmentation energies show that the Ge(SiO2)n clusters with n = 2 or 5 are stable.     

Density Functional Theory Study on the Adsorption of HCNH and CNH2 on Cu（100） Surface

The HCNH and CNH2 adsorption on different coordination sites of Cu（100） was theoretically studied considering the cluster approach. The present calculations show that the bridge site is the most favorite for CNH2 perpendicularly adsorbed on the Cu（100） surface via the C atom. For HCNH absorbed on the Cu（100） surface, the parallel adsorption mode with the C and N atoms nearly directly above the adjacent top sites of Cu（100） surface is the most favored. Both CNH2 and HCNH are strongly bound to the Cu（100） surface with CNH2 which is lightly stable （2.51 kJ·mol^-1）, indicating that both species may be co-adsorbed on the Cu（100） surface.     

Adsorption of Proline and Glycine on the TiO2(110) Surface: A Density Functional Theory Study

The optimal adsorption modes for the amino acids glycine and proline on the ideal TiO₂(110) surface are investigated by using density functional theory (PBE) applying periodic boundary conditions. Binding modes with anionic acid moieties bridging two titanium atoms after transferring a proton to the surface are the most stable configurations for both molecules investigated—similar to previous results for carboxylic acids. In contrast to the latter compounds, amino acids can form hydrogen bonds via the amino group towards the surface‐bound proton; this provides an additional stabilisation of 15–20 kJ mol^?1. Zwitterionic binding modes are less stable (by 10–20 kJ mol^?1) and are less important for proline. Neutral modes are energetically even less favourable. Calculations of vibrational frequencies and core‐level shifts complement the adsorption study and provide guidance for future experimental investigations. Control of the computational parameters is crucial for the derivation of accurate results. The layout and thickness of the slab model used are also shown to be decisive factors. Calculations with a different GGA‐functional (PW91) provide very similar relative energies, although the absolute energies change by about 20 kJ mol^?1. Results derived with the hybrid functional PBE0 show an even greater stabilisation of the anionic binding modes with respect to the zwitterionic modes. A previously observed discrepancy between experimental and theoretical results for glycine could be solved, although the experimentally proposed free rotation of the C? C bond could not be reproduced.     

簇模型ZnO(100)面上吸附CO_2的密度泛函理论研究

采用电荷自洽方法, 以嵌入原子簇Zn4O4为模型, 使用量子化学的密度泛函理论, 研究了二氧化碳在六方ZnO非极化的(1010)面的可能吸附态。计算表明, CO2垂直底物表面吸附, 氧原子只能与Zn原子配位, 并且吸附能为很弱的1.8 kJ/mol;吸附质分子平行于底物表面时, 得到了5种平衡吸附构型, 其中采用CZn配位和η2O, O二齿配位时, 吸附很弱, 经BSSE校正后的吸附能在8.8~6.6 kJ/mol。 采用η2C, O方式分别与O和Zn配位时, 吸附能为31.1 kJ/mol; C原子与表面O配位时计算得到了唯一的一个化学吸附态, 吸附能为139.6 kJ/mol, 与实验结果一致。     

(AB)_8(AB=BN, AlP, GaAs, InSb)团簇环状结构与性质的密度泛函理论研究

用杂化密度泛函B3LYP方法研究了(AB)8(AB=BN,AlP,GaAs,InSb)团簇环形结构的平衡几何构型、电子结构、振动特性以及极化率。计算结果表明,(AB)8团簇的双层环状结构中,每个A(B)原子都与3个B(A)原子成键,且Ⅴ族元素的原子比Ⅲ族元素的原子更接近团簇中心,(BN)8、(AlP)8、(GaAs)8、(InSb)8的平均极化率依次增大,IR和Raman谱峰发生红移。另外,讨论了热力学稳定性和动力学稳定性的变化。     

H2O和OH在UO(100)表面吸附的密度泛函研究

运用密度泛函理论中的广义梯度近似(GCA)的PW91方法结合周期性平板模型,研究了H2O分子和OH在UO(100)表面上的吸附.通过对不同吸附位的吸附能和几何结构参数的计算和比较发现:水分子在UO(100)表面的吸附为化学吸附,水分子平面与UO(100)表面夹角为15°的吸附构型最稳定,吸附能最大,近89 kJ·mol-1.对H2O吸附前后的态密度分析可知,H2O通过其O原子的P轨道与底物U原子的d轨道作用.本文还进一步探讨H2O在UO(100)表面的解离机理.