First principles calculations of the structural and electronic properties of(CdSe)n clusters

The structural and electronic properties of (CdSe)n(1≤n≤5) clusters are calculated using density functional theory within the pseudopotential and generalized gradient approximations. The calculated binding energies and highest occupied molecular orbital lowest unoccupied molecular orbital gaps are compared with those obtained within local density approximation.     

几种取代苯硫酚分子结构与振动光谱的理论研究

采用密度泛函理论(density functional theory, DFT)中的杂化密度泛函B3LYP方法,在6-311++G**基组水平上对几种取代苯硫酚分子的构型进行了几何优化,得出了它们的最稳定构型并对其能级差、核独立化学位移、极化率和振动光谱进行了理论计算。研究结果表明,4-巯基吡啶(4-MPY)、4-巯基苯甲酸(4-MBA)和4-巯基苯胺(PATP)均为平面构型,1,4对巯基苯(BDT)中S-H键与苯环平面的夹角为20.2°,4-甲基巯基苯(4-MBT)中S-H键与苯环平面的夹角为39.6°。几种分子都具有很强的芳香性和较大的极化率值。5种分子的极化率张量平均值大小顺序为BDT>4-MBT>4-MBA>4-MPY>PATP,极化率的各向异性不变量变化趋势为4-MBA>4-MBT>BDT>PATP>4-MPY。     

First principle studies on electronic structure and charge density of potato starch

The electronic and chemical bonding properties of biomaterial potato starch within the density functional theory are presented in this paper, with the aim to be used in electrochemical devices and biomedical applications. In the density of states and projected density of states analysis, the energy difference between the highest occupied molecular orbital and lowest unoccupied molecular orbital is reduced by 2.9 eV, which exhibits the semi-conducting behaviour of modified potato starch in the presence of NaI salt. Calculated charge density predicts the bonding properties and crystal orbital overlap population analysis exhibits the increase of amorphous nature and ionic conductivity due to sodium ion concentration. In this theoretical study, different behaviours of modified potato starch are clearly seen in the presence of NaI salt.

     

氧、硫掺杂六方氮化硼单层的第一性原理计算

采用基于密度泛函理论和投影缀加平面波的第一性原理计算方法, 研究了六方氮化硼单层(h-BN)中的氮原子缺陷(V_N)、氧原子取代氮原子(O_N)和硫原子取代氮原子(S_N)时的几何结构、磁性性质和电子结构.研究发现, V_N和O_N体系形变较小, 而S_N体系形变较大; h-BN本身无磁矩, 但具有N缺陷或者掺杂后总磁矩都是1 μ_B; 同时给出了态密度和能带结构.利用掺杂体系的局域对称性和分子轨道理论解释了相关结果, 尤其是杂质能级和磁矩的产生. 关键词： 六方BN单层 第一性原理计算 密度泛函理论 分子轨道理论     

The geometric structure and electronic properties of Fe3O3 clusters

On the basis of density-functional theory (PW91) and an all-electron numerical basis set, 60 optimized structures of Fe₃O₃⁺ clusters were obtained through optimization calculation and frequency analysis of 216 initial structures. 28 different isomers were ultimately confirmed after analyzing and re-calculating. The binding energies, the energy gaps between the highest occupied molecular orbital and lowest unoccupied molecular orbital, and the total magnetic moments of all stable isomers are reported. Some discussion of the relationship between electronic properties and structures is also presented.     

Theoretical study on the spectroscopic and third-order nonlinear optical properties of two-dimensional charge-transfer pyrazine derivatives

In this paper, density functional theory method was employed to study the electronic absorption spectrum and electronic static second hyperpolarisability of X-shaped pyrazine derivatives with two-dimensional charge-transfer structures. Computational results show that the push–pull electron abilities of the substituent groups and the length of the conjugated chains affect the electronic spectrum and static second hyperpolarisability of the pyrazine derivatives. As the push–pull electron abilities of the substituent groups or the length of the conjugated chains increases, the frontier molecular orbital energy gap decreases, resulting in increased second hyperpolarisability and redshift of the electronic absorption bands. The electronic absorption spectra of the pyrazine derivatives maintain good transparency in the blue light band. The electronic static second hyperpolarisability exhibits a linear relationship to the frontier molecular orbital energy gap. Particularly, increasing/decreasing the push–pull electron abilities of the substituent groups considerably affect the static second hyperpolarisability in long conjugated systems, which is important to the modulation of molecular organic nonlinear optical (NLO) properties. The studied pyrazine derivatives show large third-order NLO response and good transparency in the blue light band and are thus promising candidates as NLO materials for photonics applications.     

Systematic theoretical investigation of structure and electronic properties of pure copper and lithium doped copper clusters

The pure copper and lithium-doped copper clusters are studied using the unbiased CALYPSO structure searching method and density function theory to understand the evolution of various structure and electronic properties. Theoretical results show the growth behaviours of doped clusters are organised as follows: Li capped Cu_n clusters or Li substituted Cu_n+1 clusters as well as Cu capped Cu_n-1Li clusters. Moreover, the lowest energy structures of Cu_nLi favour planar structures for n ≤ 3 and three-dimensional structures for n = 4–12. In addition, the calculated averaged binding energies, fragmentation energies and second-order difference of energies exhibit obvious odd–even alternations as cluster size increasing. At last, the highest occupied-lowest unoccupied molecular orbital gaps, molecular orbital energy, magnetic property, natural population analysis, natural electron configurations, electrostatic potential, electron density difference, Infrared and Raman spectra and density of states are also, respectively, operative for characterising and rationalising the electronic properties of doped clusters.     

密度泛函理论研究CO与Nin（n=1—6）团簇的相互作用

采用密度泛函理论对CO吸附在镍团簇表面进行了系统研究.结果表明,Ni_nCO团簇的最低能量结构是在Ni_n团簇最低能量结构的基础上吸附CO生长而成,CO的吸附没有改变Ni_n团簇的结构;CO分子在Ni_n团簇表面发生的是非解离性吸附,与优化的CO键长（0.1138?nm）相比,吸附后C—O键长变长（0.1180—0.1214?nm）,表明吸附后C—O键被削弱,CO分子被活化.自然键轨道分析表明,CO分子只与最近邻的Ni原子发生相互作用;CO分子与Ni原子相互作用的本质是CO分子内的杂化轨道与Ni原子3d, 4s, 4p轨道相互作用的结果. 关键词： nCO团簇')" href="#">Ni_nCO团簇 n团簇')" href="#">Ni_n团簇 平衡结构 电子性质     

密度泛函理论研究ScnO(n=1—9)团簇的结构、稳定性与电子性质

采用基于密度泛函理论的BP86/CEP-121G （O原子采用6-311G^**基组）方法,对Sc_nO （n=1—9）团簇的几何结构、能量与稳定性、电子结构性质及其随团簇尺寸的变化趋势进行了研究.随着团簇原子个数的增加,O原子从位于Sc_n团簇结构的边缘转变为占据团簇的内部位置.O原子的掺入增加了Sc_n团簇的稳定性,使其能隙升高,并改变了其稳定性及电子结构性质随团簇尺寸变化的规律;含有偶数个Sc原子的氧化物团簇比其周围邻近的含有奇数个Sc原子的氧化物团簇具有相对较高的稳定性.Sc_nO团簇电离势的理论计算值与实验值符合得较好,而其电子亲和势呈现振荡交替上升的变化趋势;用最大化学硬度规律等方法表征了Sc_nO氧化物团簇的稳定性和电子结构性质. 关键词： nO团簇')" href="#">Sc_nO团簇 几何结构 电子性质 密度泛函理论     

Transport properties of boron-doped single-walled silicon carbide nanotubes

The doped boron (B) atom in silicon carbide nanotube (SiCNT) can substitute carbon or silicon atom, forming two different structures. The transport properties of both B-doped SiCNT structures are investigated by the method combined non-equilibrium Green’s function with density functional theory (DFT). As the bias ranging from 0.8 to 1.0 V, the negative differential resistance (NDR) effect occurs, which is derived from the great difficulty for electrons tunneling from one electrode to another with the increasing of localization of molecular orbital. The high similar transport properties of both B-doped SiCNT indicate that boron is a suitable impurity for fabricating nano-scale SiCNT electronic devices.     

理论研究B3Sin0\- (n=15-20)团簇的几何结构、稳定性和电子特性

基于B3LYP/6-311+G(d)下的密度泛函理论和卡里普索结构预测方法,系统研究了B3Sin0\- (n=15-20)团簇的几何结构、稳定性和电子特性。结构搜索发现,三个硼原子易构成三角结构并包裹在硅团簇笼子中。并通过对比实验和理论的光电子谱,进一步确定基态结构的合理性。此外,利用平均结合能、二阶差分能、最高占据轨道和最低未占据轨道能隙研究了体系的稳定性。最后,讨论了体系电荷的分布和转移、红外和拉曼谱等电子特性。     

On the properties of new benzothiazole derivatives for organic light emitting diodes (OLEDs): A comprehensive theoretical study

The present investigation explored theoretically the geometry structures, the electronic and the optical properties of new benzothiazole derivatives with incorporated triphenylamine/diphenylnaphthylamine or (4-vinylphenyl)acrylonitrile as highly efficient emitting molecular materials for organic light emitting diodes (OLEDs). This study is accomplished in order to provide an in-depth understanding of the structure-properties correlation and their effects on optoelectronic devices.In this contribution, we apply quantum-chemical methods (semiempirical Austin Model 1 (AM1), ab-initio Hartree-Fock (HF) and density functional theory (DFT)) to elucidate the photophysical properties of these molecules. First of all, the geometry structures of these compounds in the ground and the excited states were fully optimized, showing a non-planar configuration structures. Whereas, the geometrical structure of benzothiazole with cyano-PV unit is more planar. Structural parameters and vibrational properties of these compounds are then derived. Moreover, absorption and luminescence properties, lying in a bluish white or red light emission, were elucidated by ZINDO/S methods. The molecular orbital (highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)), the ionization potentials (IPs) and the electron affinities (EAs) of compounds under study were also investigated. It was found that the detailed results obtained from theoretical simulations are consistent with the available experimental data. This kind of theoretical approach has been proved to be reliable for the structure and spectroscopic properties, and predicts the favorable qualities of these benzothiazole derivatives, which make them as the materials of choice for high performance applications.     

1,8-二巯基芘分子电学特性的理论研究

在第一性原理的基础上 ,对 1,8 二巯基芘分子的电学特性进行了理论研究 .采用了 3个Au原子构成的团簇来模拟Au表面 .首先利用密度泛函理论计算了 1,8 二巯基芘分子的电子结构及其和Au表面的相互作用 ,再利用前线轨道理论和微扰理论定量地确定了该分子和Au表面的相互作用能常数 .最后利用弹性散射格林函数法研究了该分子结的伏 安特性 .计算结果表明 ,分子中的硫原子和Au原子形成很强的共价键 .当外加偏压小于 1V时分子结存在电流禁区 ,随着偏压升高 ,分子结的电导出现平台结构 .分子结的电导特性和其电子结构密切相关 ,扩展分子轨道为电荷的迁移提供了通道 ,而局域轨道对电流贡献很小     

First-principles study of the optical properties of defect electronic structure and chalcopyrite CdGa2Te4

<正>The electronic and optical properties of the defect chalcopyrite CdGa₂Te₄ compound are studied based on the first-principles calculations.The band structure and density of states are calculated to discuss the electronic properties and orbital hybridized properties of the compound.The optical properties,including complex dielectric function,absorption coefficient,refractive index,reflectivity,and loss function,and the origin of spectral peaks are analysed based on the electronic structures.The presented results exhibit isotropic behaviours in a low and a high energy range and an anisotropic behaviour in an intermediate energy range.     

SimGen(m+n=9)团簇结构和电子性质的计算研究

硅锗团簇结构与电子性质的研究对于研发新型微电子材料具有重要意义. 将遗传算法和基于密度泛函理论的紧束缚方法相结合, 研究了Si_mGe_n(m+n=9)团簇的原子堆积结构和电子性质. 计算结果发现, Si_mGe_n(m+n=9) 团簇存在两种低能原子堆积稳定构型: 带小金字塔的五边形双锥堆积和带桥位Ge原子的四面体紧密堆积. 随着团簇内锗原子数目的逐渐增加, 两种堆积结构均出现明显的转变, 其中最低能量的几何结构由单侧带相邻双金字塔的五边形双锥结构转变为双侧带相邻单金字塔的五边形双锥结构. 随着原子堆积结构的变化, 团簇内原子电荷分布及电子最高占据轨道与电子最低未占据轨道的能隙随团簇内所含硅和锗元素组分的不同呈现出明显的差异.     

The geometry structures and electronic properties of Li_mB_n(m+n=12) clusters

The geometric structures, electronic properties, total and binding energies, harmonic frequencies, the highest occupied molecular orbital to the lowest unoccupied molecular orbital energy gaps, and the vertical ionization potential energies of small LimBn （m＋ n = 12） clusters were investigated by the density functional theory B3LYP with a 6-31 I＋G （2d, 2p） basis set. All the calculations were performed using the Gaussian09 program. For the study of the LimBn clusters, the global minimum of the B 12 cluster was chosen as the starting point and the boron atoms were gradually replaced by Li atoms. The results showed that as the number of Li atoms increased, the stability of the LimBn cluster decreased and the physical and chemical properties became more active. In addition, on average there was a large charge transfer from the Li atoms to the B atoms.     

Structural and electronic properties of lithium endohedral doped carbon nanocapsules

Endohedral lithium and lithium ion doped carbon nanocapsule (CNC) systems have been theoretically investigated by performing semi-empirical molecular orbital method at the level of PM3 (UHF and/or RHF) type quantum chemical treatment in order to explore the energetics and electronic structures. The geometries of the studied systems have been optimized and the molecular properties, energies, some selected molecular orbital eigenvalues and dipole moments of the studied capsules are reported. Molecular dynamics simulations have been also performed to study the structural properties and energetics of endohedral lithium and lithium ion doped CNCs.     

NpFn分子结构与电子结构的理论研究

运用杂化密度泛函(B3LYP)方法,对NpFn(n=3~6)的分子结构特性进行了系统地研究.优化得到了各分子的平衡几何构型,计算了分子的振动频率,并进行了态密度和自然键价轨道(NBO)分析.讨论了不同芯电子相对论有效原子芯势(RECP)对计算结果的影响,分析了NpFn分子的成键,发现随着与Np结合的F原子数目增加,Np原子的5f与F原子的2p轨道能逐渐接近,成键依次增强,键长呈现出收缩的趋势.目前的计算结果与可行的理论和实验符合较好.     

Electronic energy levels of weakly coupled nanostructures: C60-metal interfaces

A new approach based on density functional theory and the Anderson impurity model is developed to calculate charging energies and quasiparticle energy gaps of molecular systems weakly coupled to an environment. The approach is applied to C60 adsorbed on Au(111) and Ag(100) surfaces, resulting in electronic structures that are in excellent agreement with recent experiments. Image-charge screening effects on molecular orbital energies are found to be of similar magnitude for the two surfaces, but charge-transfer screening and spin fluctuations also affect the Ag case due to a partially occupied C60 orbital.     

(Zn,Al)O电子结构第一性原理计算及电导率的分析

采用第一性原理平面波赝势方法和广义梯度近似计算了ZnO与(Zn,Al)O的电子结构.结合分子轨道理论,从原子布居、键布居、能带结构和态密度角度分析了掺Al前后ZnO的成键情况及对电子间相互作用的影响.利用第一性原理计算结果理论推导计算了(Zn,Al)O的载流子浓度并进一步分析了ZnO电导率的变化情况.与实验结果比较可知,掺Al后ZnO载流子浓度增加,并且ZnO的电导率比未掺杂时有了显著的提高. 关键词： 第一性原理 电子结构 电导率 (Zn Al)O