苯系物Cu_3金属配合物的结构与性质的理论研究

采用密度泛函理论的B3LYP方法，在6-311+G(d,p)基组水平上计算研究了Cu_3团簇与甲苯、二甲苯、三甲苯分子作用的各种异构体结构和频率，比较各异构体间的能量关系，得到最稳定的几何构型．通过分析Cu_3和苯系列化合物作用的结合能和前线轨道等性质，从而了解该类配合物的作用机理.     

铜苯配合物结构与性质的理论研究

采用密度泛函理论的B3LYP、BP86、BPW91、B3PW91四种方法,在6-311+G(d,p)基组水平上计算研究了Cu_n(n=1-6)团簇与Cu_nC_6H_6(n=1-6)配合物的各个异构体结构和频率,比较各异构体间的能量关系,得到最稳定的几何构型.通过分析铜苯配合物的结合能和前线轨道等性质,从而了解该类配合物的作用机理.     

关于YBa_2Cu_3O_x-PrBa_2Cu_3O_x-YBa_2Cu_3O_x多层膜的研究

采用磁控溅射法研制了 YBa_2Cu_3O_x-PrBa_2Cu_3O_x-YBa_2Cu_3O_x 多层外延膜.上、下 YBa_2·Cu_3O_x 层的零电阻转变温度分别是80K 和82K.在77K 测量得到 PrBa_2Cu_3O_x 隔离层的电阻率约为 8×10~4Ω·cm.     

YBa_2Cu_3O(7-δ)/势垒层/YBa_2Cu_3O_(7-δ)三层结构的制备

本文采用射频磁控溅射法分别以 CeBa_2Cu_3O_(7-δ)和 MgO 为势垒层,原位制备出 YBa_2Cu_3.O_(7-δ)/CeBa_2Cu_3O_(7-δ)/YBa_2Cu_3O_(7-δ)和 YBa_2Cu_3O_(7-δ)/MgO/YBa_2Cu_3O_(7-δ)三层结构.文中给出了一些初步的实验结果,它们表明:在 YBa_2Cu_3O_(7-δ)薄膜与势垒层之间有较严重的互扩散.     

Cu_2O/ZnO氧化物异质结太阳电池的研究进展

介绍了近年来低成本Cu_2O/ZnO氧化物异质结太阳电池方面的研究进展.应用于光伏器件的吸收层材料Cu_2O是直接带隙半导体材料,天然呈现p型;其原材料丰富,且对环境友好.Cu_2O/ZnO异质结太阳电池结构主要有平面结构和纳米线/纳米棒结构.纳米结构的Cu_2O太阳电池提高了器件的电荷收集作用;通过热氧化Cu片技术获得的具有大晶粒尺寸平面结构Cu_2O吸收层在Cu_2O/ZnO太阳电池应用中展现出了高质量特性.界面缓冲层(如i-ZnO,a-ZTO,Ga_2O_3等)和背表面电场(如p~+-Cu_2O层等)可有效地提高界面处能级匹配和增强载流子输运.10 nm厚度的Ga_2O_3提供了近理想的导带失配,减少了界面复合;Ga_2O_3非常适合作为界面层,其能够有效地提高Cu_2O基太阳电池的开路电压V_(oc)(可达到1.2 V)和光电转换效率.p~+-Cu_2O(如Cu_2O:N和Cu_2O:Na)能够减少器件中背接触电阻和形成电子反射的背表面电场(抑制电子在界面处复合).利用p型Na掺杂Cu_2O(Cu_2O:Na)作为吸收层和Zn_(1-x)Ge_x-O作为n型缓冲层,Cu_2O异质结太阳电池(器件结构:MgF_2/ZnO:Al/Zn_(0.38)Ge_(0.62)-O/Cu_2O:Na)光电转换效率达8.1%.氧化物异质结太阳电池在光伏领域展现出极大的发展潜力.     

{Cu_3}单分子磁体在热平衡和磁场作用下的三体纠缠

本文研究了Na_9[Cu_3Na_3(H_2O)_9(α-As W_9O_(33))_2]·26H_2O(简记为{Cu_3})单分子磁体在热平衡和外加磁场作用下的三体纠缠性质,利用等效自旋模型和实验拟合参数,数值计算了{Cu_3}型三角自旋环中三体负性纠缠度(tripartite negativity).分别考虑沿垂直于三角自旋环方向的磁场、平行于三角自旋环方向的磁场,以及倾斜磁场的情形.结果表明,磁场的方向、大小以及温度对系统三体负性纠缠度有着重要影响.文中给出了在不同磁场方向下,临界温度随磁场强度的变化图,由此可以得到三体纠缠存在的参数区域.同时发现在特定的参数区域,该系统存在纠缠恢复现象.因此适当调节温度、磁场强度大小和磁场方向可以有效调控{Cu_3}型三角自旋环中的三体纠缠性质.     

融熔织构生长的YBa_2Cu_3O_(7-x)的微结构与缺陷

本文主要用 TEM 方法研究了融熔织构生长(MTG)的 YBa_2Cu_3O_(7-x)块样的微结构和缺陷.指出 MTG-YBCO 材料由平行 ab 面的片状晶体组成.在片状结构内部除了123相外,还频繁交替出现 Y_2Ba_4Cu_3O_(16)(248)和 Y_2Ba_2Cu_4O_y(224)等类型的层状堆垛缺陷.这种择优取向的片状组织和层状缺陷有利于超导电流的传输,同时对磁力线起钉扎中心的作用,是 J_c 值提高的两个结构因素.     

GdBa_2Cu_(3-x)CO_xO_y、NdBa_2Cu_(3-x)CO_xO_y 的超导电性

采用固相反应法制备了单相元素替代超导氧化物系列 GdBa_2Cu_(3-x)Co_xO_y,NdBa_2Cu_(3-x)Co_xO_y对这些样品的晶格常数和电阻-温度关系进行了测量,发现随掺杂量 x 的增加,①两系列样品均呈现出金属-半导体转变;②NdBa_2Cu_(3-x)Co_xO_y 出现一从正交到四方的结构相变,并且在发生该相变之前,超导电性已消失;③GdBa_2Cu_(3-x)Co_xO_y 的 T_c(x)随 x 变化近似成线性关系.取适当的 x_(cr),与 AG 曲线比较,发现在高含量区出现偏差.将本实验结果与 YBa_2Cu_(3-x)Co_xO_(7-δ)、YBa_2Cu_(3-x)Fe_xO_(7-δ),YBa_2Cu_(3-x)Ni_xO_(7-δ),GdBa_2Cu_(3-x)Fe_xO_(7-δ)等系列相应的结果作比较,认为磁性稀土元素与固有磁矩较大的过渡元素间很可能存在某种磁相互作用.同时还讨论了其它可能的拆对机制.     

N9H9链状异构体的结构与稳定性的理论研究

采用密度泛函理论(DFT)B3LYP方法,在6-311++G**基组水平上对N9H9可能存在的链状异构体进行了几何优化,得到46种稳定链状异构体.应用自然键轨道理论NBO和分子中的原子理论AIM分析了这些链状异构体的成键特征和相对稳定性,G3MP2方法计算了各异构体的精确能量及在298K时的生成热△fH°(298 K),并计算了由Peter Politzer等人所介绍的相对比冲量.研究蛄果表明:各异构体中N原子孤对电子与N=N形成了P→π共轭作用是影响双键相邻的N-N键长变化的主要原因,并且对异构体的稳定性起着重要作用.所有异构体中N=N位于链端的稳定性较兰,其中B9最稳定,B6稳定性最差;C5是所有异构体中生成热最大的,也是相对比冲量最大的.     

内在缺陷与Cu掺杂共存对ZnO电磁光学性质影响的第一性原理研究

采用基于自旋密度泛函理论的平面波超软赝势方法,研究了Cu掺杂ZnO (简称Cu_(Zn))与内在缺陷共存对ZnO电磁光性质的影响.结果表明,Cu是以替位受主的形式掺入的;制备条件对Cu_(Zn)及内在缺陷的形成起至关重要的作用,富氧条件下Cu掺杂有利于内在缺陷的形成,且Cu_(Zn)-O_i最易形成;相反在缺氧条件下,Cu掺杂不利于内在缺陷的形成.替位Cu的3d电子在价带顶形成未占据受主能级,产生p导电类型.与Cu_(Zn)体系相比,Cu_(Zn)-V_O体系中载流子浓度降低,导电性变差;Cu_(Zn)-V_(Zn)体系中载流子浓度几乎不变,对导电性没影响;Cu_(Zn)-O_i体系中载流子浓度升高,导电性增强.纯ZnO体系无磁性;而Cu掺杂ZnO体系,与Cu原子相连的O原子,电负性越小,键长越短,对磁矩贡献越大;Cu_(Zn)与Cu_(Zn)-O_i体系中的磁矩主要是Cu的3d电子与Z轴上O的2p电子耦合产生的;Cu_(Zn)中存在空位缺陷(V_O,V_(Zn))时,磁矩主要是Cu 3d电子与XY平面内O的2p电子强烈耦合所致;Cu_(Zn)中存在V_(Zn)时,磁性还包含V_(Zn)周围0(5, 6)号原子2p轨道自旋极化的贡献;所有体系中Zn原子自旋对称,不产生磁性.Cu_(Zn)-V_(Zn)和Cu_(Zn)-O_i缺陷能态中,深能级中产生的诱导态是0-0 2s电子相互作用产生的.Cu_(Zn)模型的光学带隙减小,导致吸收边红移;Cu_(Zn)-V_(Zn)模型中吸收和反射都增强,使得透射率降低.     

A density functional theory study on the adsorption of CO and O₂ on Cu-terminated Cu₂O（111） surface

The adsorptions of CO and O2 molecules individually on the stoichiometric Cu-terminated Cu2O(111) surface are investigated by first-principles calculations on the basis of the density functional theory.The calculated results indicate that the CO molecule preferably coordinates to the Cu2 site through its C atom with an adsorption energy of -1.69 eV,whereas the O2 molecule is most stably adsorbed in a tilt type with one O atom coordinating to the Cu2 site and the other O atom coordinating to the Cu1 site,and has an adsorption energy of -1.97 eV.From the analysis of density of states,it is observed that Cu 3d transfers electrons to 2π orbital of the CO molecule and the highest occupied 5σ orbital of the CO molecule transfers electrons to the substrate.The sharp band of Cu 4s is delocalized when compared to that before the CO molecule adsorption,and overlaps substantially with bands of the adsorbed CO molecule.There is a broadening of the 2π orbital of the O2 molecule because of its overlapping with the Cu 3d orbital,indicating that strong 3d-2π interactions are involved in the chemisorption of the O2 molecule on the surface.     

Classical trajectory calculations of the energy distribution of ejected atoms from ion bombarded single crystals

The energy distribution of particles ejected from single crystal surfaces has been calculated using classical dynamics. The model utilizes a microcrystallite of 4 layers with ~60 atoms/layer which is bombarded by 600 eV Ar⁺ at normal incidence. Calculations have been performed for the clean (100) face of copper as well as for copper with oxygen placed in various coverages and site geometries. The energy distributions for Cu, O, Cu₂, CuO and Cu₃ are reported for this system. The distribution for clean Cu exhibits structure which is shown to arise from preferred ejection mechanisms in the crystal. For oxygen adsorbates, the effect of the oxygen binding energy on the peak in the energy distribution of the ejected oxygen atoms is examined by arbitrarily varying the well-depth of the Cu-O pair potential. In general, higher values of the binding energy produce a maximum in the curve at higher energies and also produce a broader energy distribution. The O₂ and Cu₂ dimer distributions are found to peak at approximately the same energy as the O and Cu curves when compared on a kinetic energy/particle basis, although their widths are considerably smaller. Finally, we predict that the CuO energy distribution should be wider than either the Cu₂ or O₂ distributions since it results from the convolution of the Cu and O distributions which are quite different.     

Shallow donor states induced by in-diffused Cu in ZnO: a combined HREELS and hybrid DFT study

A combined experimental and first principles study of Cu defects in bulk ZnO is presented. Cu particles are epitaxially deposited on the polar O-ZnO(0001) surface at room temperature. Upon heating, a broadening of the quasielastic peak in high resolution electron energy loss spectra is observed, corresponding to an electronic doping effect of Cu atoms in bulk ZnO with an ionization energy of 88 meV. Cu impurities in ZnO, although commonly acting as acceptors, are presently observed to induce shallow donor states. We assign these to interstitial Cu species on the basis of a hybrid density functional study.     

ZnS∶Cu-罗丹明B的荧光共振能量转移性质

为了解决现有的基于量子点荧光共振能量转移体系的生物毒性问题,选用无毒的ZnS∶Cu量子点与罗丹明B构建新型荧光共振能量转移体系。通过共沉淀法成功制备了形貌均一的ZnS∶Cu纳米晶量子点。在此基础上,测试了不同掺杂浓度的ZnS∶Cu量子点及罗丹明B的荧光光谱。然后,通过对ZnS∶Cu量子点的表面修饰构建了以ZnS∶Cu量子点为供体、罗丹明B为受体的荧光共振能量转移体系。实验结果表明:ZnS∶2%Cu量子点的发光光谱与罗丹明B的吸收光谱在481 nm处有较大重合,说明构建荧光共振能量转移的最佳铜掺杂摩尔分数为2%。通过计算发现以ZnS∶2%Cu量子点为供体、罗丹明B为受体的荧光共振能量转移体系的能量转移效率为25.8%。进一步实验结果表明,罗丹明B浓度也能够影响能量转移。     

Is the (hfac)Cu(I)–(tmvs) bond intrinsically weak?

Density functional theory studies were performed to study the structure and bonding of (hexafluoroacetylacetonate)-copper(I)-(trimethylvinylsilane) [Cu(hfac)(tmvs)], an ideal and important Cu(I)-CVD compound. A popular three-parameter hybrid density functional (B3LYP) with 6-311+G(d,p) and an effective core potential included LanL2DZ basis set was utilized for this purpose. The (hfac)Cu–(tmvs) bond energy of approximately 30?kcal?mol^?1 obtained at the B3LYP/6-311+G(d,p) level of theory reveals that the Cu–olefin bond in Cu(hfac)(tmvs) is not as weak as previously estimated/assumed and, hence, that the substrate plays a vital role in copper film formation from Cu(hfac)(tmvs). Bonding analysis reveals that fairly strong (hfac)Cu–(tmvs) bonding is the result of DCD-model σ-donation and π-back-bonding between the copper and tmvs in Cu(hfac)(tmvs).     

Combinative energy, oxygen deficiency and superconductivity in LnBa2Cu3O7-x （Ln=Nd, Er, Sm）

The correlation among the combinative energy, superconductivity, oxygen content, the position of holes in different planes, and the position of holes in the Cu(2)-O plane in LnBa2Cu3O7-x (Ln=Nd, Er, and Sin) has been investigated on the basis of a block model. The results indicate that the combinative energy decreases with increasing Tc in all of these compounds. And also, the combinative energies are obviously different with holes at different positions in the Cu(2)-O plane when the oxygen deficiency is low. However, this difference becomes less with increasing the oxygen deficiency.The effect of the holes in different positions on the combinative energy supplies some clue to the understanding of an unresolved problem, i.e. whether the distribution of carriers in the CuO2 plane is uniform or inhomogeneous. The results not only show that the structural characters, the combinative energy between two structural blocks and the superconductivity are closely interrelated in this class of compounds, but also reveal some differences among these systems. The relationship between the combinative energy and the Tc value in NdBa2Cu3O7-x shows some features different from the systems containing Er or Sm.     

Cluster and periodic DFT calculations of adsorption and activation of CO2 on the Cu(hkl) surfaces

The adsorption behavior and thermal activation of carbon dioxide on the Cu(1 1 1), Cu(1 0 0), and Cu(1 1 0) surfaces have been investigated by means of density functional theory calculations and cluster models and periodic slabs. According to the cluster models, the optimized results indicate that the basis set of C and O atoms has a distinct effect on the adsorption energy, but an indistinct one on the equilibrium geometry. For the CO₂/Cu(hkl) adsorption systems studied here, the final structure of adsorbed CO₂ is near linear and the preferred modes for the adsorption of CO₂ onto the Cu(1 1 1), Cu(1 0 0), and Cu(1 1 0) surfaces are the side-on adsorption at the cross bridge site with an adsorption energy of 13.06 kJ/mol, the side-on adsorption at the short bridge site (13.54 kJ/mol), and the end-on adsorption on the on-top site with C–O bonds located along the short bridge site (26.01 kJ/mol), respectively. However, the calculated adsorption energies from periodic slabs are lower as compared to the experimental data as well as the cluster model data, indicating that the periodic slab approach of generalized gradient approximation in the density function theory may be not suitable to obtain quantitative information on the interaction of CO₂ with Cu(hkl) surfaces.     

多壳层铜纳米线结构和电子特性的第一性原理研究

基于密度泛函理论框架下的第一性原理计算,系统地研究了多壳层Cu纳米线的稳定结构和电子特性.得到不同线径多壳层Cu纳米线的平衡态晶格常数相差不大,都表现出金属特性,且其单原子平均结合能和量子电导随着纳米线直径的增加而增加.纳米线中内壳层Cu原子表现出体相结构Cu原子相似的电子特性,而表面壳层由于配位数的减少,其3d态能量范围变窄且整体向费米能级发生移动.电荷密度分析表明,相对于体相Cu晶体中原子间的相互作用,纳米线表面壳层Cu原子与其最近邻原子间的相互作用明显增强.     

铁铜双核羰基簇合物结构的理论研究

采用密度泛函理论BPW91方法在6-311+G(d)基组水平上, 对FeCu团簇吸附CO过程中可能的几何结构和电子态进行了系统研究. 计算结果表明: FeCu双原子团簇饱和吸附CO分子数是7, 配位过程均为放热反应, 吸附能最大的结构是FeCu(CO)1. 金属原子满足18电子规则,对CO的吸附位置起主要决定作用, 即CO配位由于遵循18电子规律, 即Fe原子上形成Fe(CO)4Cu 之后CO与Cu原子发生配位形成Fe(CO)4Cu(CO)3. 各配合物中 Fe电荷密度最大的结构是Fe(CO)4Cu(CO)1, Cu电荷密度最大的结构Fe(CO)4Cu(CO)3.