Ab Initio Calculations of the Electronic Structures of Copper Pyrites CuS2, CuSe2 and CuTe2

The electronic structures of CuS2, CuSe2 and CuTe2 with pyrite structures, within the framework the density-functional theory have been investigated. The calculated results explained the recent experimental results which show that there is no clear indication of strong electron correlations in the electronic properties of Cu pyrites, due to the dominant chalcogen p character rather than d characteristic of Cu at the Fermi level.

Elastic properties and electronic structures of lanthanide hexaborides

The structural, elastic, and electronic properties of a series of lanthanide hexaborides（Ln B6） have been investigated by performing ab initio calculations based on the density functional theory using the Vienna ab initio simulation package.The calculated lattice and elastic constants of Ln B6 are in good agreement with the available experimental data and other theoretical results. The polycrystalline Young＇s modulus, shear modulus, the ratio of bulk to shear modulus B/G, Poisson＇s ratios, Zener anisotropy factors, as well as the Debye temperature are calculated, and all of the properties display some regularity with increasing atomic number of lanthanide atoms, whereas anomalies are observed for Eu B6 and Yb B6. In addition, detailed electronic structure calculations are carried out to shed light on the peculiar elastic properties of Ln B6.The total density of states demonstrates the existence of a pseudogap and indicates lower structure stability of Eu B6 and Yb B6 compared with others.

The stabilities, electronic structures and elastic properties of Rb-As systems

The structural, electronic and elastic properties of Rb As systems （RbAs in NaP, LiAs and AuCu structures, RbAs2 in the MgCu2 structure, Rb3As in NaaAs, Cu3P and Li3Bi structures, and Rb5As4 in the A5B4 structure） are investigated with the generalized gradient approximation in tile frame of density functional theory. The lattice parameters, cohesive energies, formation energies, bulk moduli and the first derivatives of the bulk moduli （to fit Murnaghan＇s equation of state） of the considered structures are calculated and reasonable agreement is obtained. In addition, the phase transition pressures are also predicted. The electronic band structures, the partial densities of states corresponding to the band structures and the charge density distributions are presented and analysed. The second-order elastic constants based on the stress-strain method and other related quantities such as Young＇s modulus, the shear modulus, Poisson＇s ratio, sound velocities, the Debye temperature and shear anisotropy factors are also estimated.

<i>Ab-Initio</i>Calculations of 27 Electronic States of the BP⁺Ion-Molecule

The theoretical investigation of the potential energy curves, in the representation 2s+1Λ(+/-), of the 27 low-lying Doublet and Quartet electronic states of the BP+ molecular ion has been performed with the methods in quantum chemistry, the Complete Active Space Self Consistent Field (CASSCF) and the Multireference Configuration Interaction (MRCI) calculations. The harmonic vibrational frequency ωe, the inter-nuclear distance at equilibrium Re, the rotational constant Be, the electronic energy with respect to the minimum ground state energy Te, and the permanent dipole moment have also been calculated. Twenty-three new electronic states have been investigated here for the first time. The comparison between the values of the present work and those available in the literature for several electronic states shows a good agreement. These investigated data can be a conducive to further work on BP+ molecular ion in both experimental and theoretical research.

Electronic and Optical Properties of Rare Earth Oxides: <i>Ab Initio</i>Calculation

In this work, we have investigated the electronic and optical properties of the technologically important rare earth oxide compounds—X2O3 (X: Gd, Tb) using the density functional theory within the GGA. The band structure of X2O3 have been calculated along high symmetry directions in the first brillouin zone. The real and imaginary parts of dilectric functions and the other optical responses such as energy-loss function, the effective number of valence electrons and the effective optical dielectric constants of the rare earth sesquioxides (Gd2O3 and Tb2O3) were calculated.

Ab Initio Calculation of the Electronic States of ScTe Molecule below 19,500 cm-1

The potential energy curves (PECs) of the16 lowest electronic states in the representation 2s+1Λ (+/-) of the molecule ScTe have been investigated via ab initio CASSCF and MRCI (single and double excitations with Davidson correction) calculations. The permanent dipole moment curves (PDMCs) and the spectroscopic constants such as vibrational harmonic frequency ωe, the internuclear distance at equilibrium Re, the rotational constant Be, and the electronic transition energy Te with respect to the ground state have been calculated for the different bound investigated electronic states. The comparison of the present results with the rare available theoretical data in literature shows an overall good agreement. To the best of our knowledge, 15 electronic states of the ScTe molecule are not yet investigated either experimentally or theoretically, they are investigated in the present work for the first time.

亚甲二醇二硝酸酯构型和电子结构的 ab initio 研究

采用量子化学中的从头计算（ａｂｉｎｉｔｉｏ）方法，在ＨＦ／３－２１Ｇ和ＨＦ／６－３１Ｇ＊水平上分别计算研究了亚甲二醇二硝酸酯（ＭＧＤＮ）的旋转构象和电子结构，计算所得ＭＧＤＮ绕Ｃ—Ｏ键旋转的能垒较低（约６ｋＪ／ｍｏｌ），其平面构象的能量最高．能量最低的构象（亦即最稳定构型或平衡几何构型）的２个酯基均绕Ｃ—Ｏ键旋转７７．４°．不同构型的电荷分布差异较小．

Uncovering the Phase Transition of Berlinite (α-AlPO_(4)) under High Pressure:Insights from First-principles Calculations

We investigated the mechanism of crystalline-to-amorphous phase transition(CAPT)for amorphous berlinite(a-AlPO_(4))under high pressure using ab initio constant-pressure techniques.Our results show that the pressure to the change in phase transition takes place at around 20 GPa,which is inconsistent with the previous results of around 15 GPa.To confirm the feasibility of our model,the calculated X-ray powder diffraction for crystal berlinite is concordant with the standard PDF card.By assessing a full spectrum of properties including atomic structure,bonding characteristics,electron density of states and real-space pair distribution function at each pressure,we reveal the details of phase transition.Importantly,all the information from our present results elucidates that Al-O bonds play an irreplaceable role during the process of phase transition to uncover the structural and electronic properties of berlinite.Overall,our work substantiates that it is essential to utilize a wide range of changes in order to provide a comprehensive understanding on the nature of the CAPT in other inorganic oxides.

First Principles Study on NaxLi1-xFePO4 As Cathode Material for Rechargeable Lithium Batteries

电子结构和离子的动态性质纯并且做的 Na (李地点) LiFePO4 被第一原则的计算调查了。Nadoped 材料的乐队差距比 undoped 那的狭窄，更好电子的传导性的性质显示。第一原则的基于的分子的动态模拟被执行了为李离子散开检验迁居精力障碍。显示出的结果为李散开的精力障碍沿着一个维的散开小径有点减少了，显示离子的传导性的性质是也改善了，作为与做的高挂布相比(例如 Cr ) 案例。

Theoretical Calculation of the Low-Lying Electronic States of the Molecule BaS

Complete Active Space Self Consistent Field (CASSCF) with Multireference Configuration Interaction (MRCI) and Rayleigh-Schrodinger Perturbation Theory (RSPT2-RS2) methods have been used to investigate the potential energy curves for the 12 low-lying singlet and triplet electronic states in the representation 2s+1Λ(+/-) of the molecule BaS with Davidson corrections. The harmonic frequency we, the internuclear distance Re, the electronic energy with respect to the ground state Te, the rotational constants Be and the permanent dipole moment have been calculated for these electronic states. The eigenvalues Ev, the rotational constants Bv, the centrifugal distortion constant Dv and the abscissas of the turning points Rmin and Rmax have been investigated using the canonical functions approach. Nine new electronic states have been investigated here for the first time. The comparison between the values of the present work and those available in the literature for several electronic states shows a good agreement.

Electronic Structure and Spectroscopic Studies of the Molecule ScS

Theoretical investigation of the lowest electronic states of ScS molecule, in the representation 2s+1Λ(+/-), has been performed via CASSCF and MRCI (single and double excitations without Davidson correction) calculations. The calculated potential energy curves (PECs), permanent dipole moment curves (PDMCs), and spectroscopic constants are reported for the 10 lowest electronic states. The eigenvalues Ev, the rotational constants Bv, and the centrifugal distortion constants Dv have been calculated for various vibrational levels. The comparison of the present results with the available experimental data in literature shows an overall good agreement. To the best of our knowledge, 6 electronic states of the ScS molecule, between 11600 cm-1 and 15000 cm-1 are not yet observed experimentally and are investigated in the present work for the first time.

Theoretical Calculation of the Low-Lying Electronic States of the Molecule ScSe

Theoretical investigation of the lowest electronic states of ScSe molecule, in the representation 2s+1Λ(+/-), has been performed via CASSCF and MRCI + Q (single and double excitations with Davidson correction) calculations. The calculated potential energy curves (PECs), permanent dipole moment curves (PDMCs), and spectroscopic constants are reported for the 14 lowest electronic states. The comparison of the present results with the rare available theoretical data in literature shows an overall good agreement. To the best of our knowledge, 13 electronic states of the ScSe molecule are not yet investigated either experimentally or theoretically;they are investigated in the present work for the first time.

Theoretical Study of the Triplet Electronic States of the BP Molecule

The Complete Active Space Self Consistent Field (CASSCF) with Multi Reference Configuration Interaction (single and double excitation with Davidson correction) MRCI + Q method has been used to investigate the potential energy curves of the 17 low-lying triplet electronic states of the molecule BP. The harmonic vibrational frequency ωe, the inter-nuclear distance at equilibrium Re, the rotational constant Be, the electronic energy with respect to the minimum ground state energy Te, and the permanent dipole moment have been also calculated. A literature review shows a strong correlation between our investigated data and those previously published either theoretically or experimentally. This work introduces, for the first time, a study of 14 new electronic states. Our spectroscopic data can be a conducive to further work on BP molecule in both experimental and theoretical research.

Recalculate Structural, Elastic, Electronic, and Thermal Properties in LaAlO₃Rhombohedral Perovskite

We study the structural, elastic and electronic properties of perovskite insulator LaAlO3 using two different methods: the full-potential linearized augmented plane wave method and the pseudo-potential plane wave scheme in the frame of generalized gradient approximation and local density approximation GGA + mBJ. We have evaluated the ground state quantities. Also, we have presented the results of the band structure and densities of states. These results are in favourable agreement with previous theoretical works and the existing experimental data. To complete the fundamental characteristics of this compound, we have analyzed the thermodynamic properties.

草酰胺桥联双核铜配合物Cu_2(oxen)(SCN)_2从头算研究

运用Caussian94W量子化学程序包，采用LanL2DZ基组，对草酰胺桥联双核铜配合物Cu2（oxen）（SCN）2［H2oxen＝N，N’－二－（2－胺乙基）草酰胺］顺、反构型及其单、三重态的电子组态进行从头算研究，探讨其配合物的稳定性、分子轨道能量、原子净电荷布居规律以及电子结构特征等。结果表明：在Cu2（oxen）（SCN）2分子的4种可能的构型与组态中，最稳定的是反式三重态构型，其原因是该构型的中心对称性有利于电子云的均匀分布，从而使trans－式分子轨道能量比cis－式相应的分子轨道能量低。结果还表明：草酸胺分子的桥联作用大体上没有改变Cu原子的自旋布居，但却起着传递自旋电子的重要作用，计算结果与实验规律相符。

草酰胺桥联双核铜配合物结构单元的从头算

运用Gaussian 94W量子化学程序包 ,采用LanL2DZ基组 ,对草酰胺桥联双核铜配 (聚 )合物结构单元Cu2 (oxen) (OH) 2 [H2 oxen =N ,N' 二 ( 2 胺乙基 )草酰胺 ](包括顺、反构型及其单、三重态电子组态 )进行从头算研究 ,探讨该配合物结构单元的稳定性 ,并从电荷布居及分子轨道组成等电子结构特征分析这种配合物反式三重态比较稳定的原因 .计算结果与实验规律相符合 .

~7LiH分子的基态X^1Σ^+和激发态A^1Σ^+、B^1Π与b^3Π的平衡几何与垂直激发能

使用分子反应静力学的有关原理,推导出了7L iH分子的基态X1Σ+、单重态的第一激发态A1Σ+、第二激发态B1Π以及三重态的第二激发态b3Π的合理离解极限.利用“对称性匹配蔟-组态相互作用”方法,在完全活性空间中计算了这一分子相应于上述各态的平衡核间距.其中,X1Σ+态为0.160 9 nm;A1Σ+和B1Π态分别为0.248 7和0.243 4 nm;b3Π态为0.195 8 nm.在基态的平衡位置处,计算了从基态到A1Σ+、B1Π及b3Π态的垂直激发能,其值分别为3.613、4.612和4.233 eV.将本文获得的计算结果与其它理论方法获得的计算结果及实验结果进行了比较,计算结果与实验结果吻合得很好;同时,本文获得的平衡核间距和垂直激发能与使用很复杂的方法获得的计算结果也相当接近.

闪锌矿GaN(001)表面的电子结构

采用混合基表示的第一原理赝势方法 ,计算了闪锌矿结构的 Ga N(0 0 1) (1× 1)干净表面的电子结构 .分析了得到的各原子分态密度、面电荷密度分布以及表面能带结构等性质 ,比较了 Ga N(0 0 1)的 Ga端表面和 N端表面两种情况 .结果显示 ,闪锌矿 Ga N(0 0 1)的 Ga端表面比 N端表面更稳定 ,这两种 (1× 1)表面都是金属特性 .此外 。

Mo_2[(p-tol)NCHN(p-tol)]_4及其阳离子电子结构和电子吸收光谱的从头算研究

用密度泛函理论中的 B3 LYP方法 ,采用 Lan L2 DZ基组 ,对 Mo2 (form) 4和 [Mo2 (form) 4]+ {其中(form) -=[(p-tol) NCHN(p-tol) ]-) },进行了分子轨道计算 ,明确了 Mo— Mo键具有σ2 π4 δ2 四重键的性质 .计算得到 Mo— Mo间的分子轨道顺序为π<σ<δ<σ* <δ* <π* .用单激发组态相互作用 (CIS)方法计算了 Mo2 (form) 4和 [Mo2 (form) 4]+ 的电子吸收光谱 ,Mo2 (form) 4的最低能吸收光谱λ=3 90 nm,是 1A1g→ 1Eg跃迁产生的 ,属于金属内部的电荷迁移 .[Mo2 (form) 4]+ 的最低能吸收光谱 λ=1 0 96nm,也是 1Ag→ 1Eg 跃迁产生的 。

N,N′-亚水杨基皮考林酰肼合铜的晶体结构及荧光性质

在DMF和CH3 OH中 ,以N ,N′ 亚水杨基皮考林酰肼 (简写为H2 sphz)和高氯酸铜合成了双核配合物[Cu2 (sphz) (DMF) 3 H2 O]·(ClO4) 2 。X射线衍射实验结果表明 ,标题配合物晶体属于单斜晶系 ,空间群为P2 1/c,分子式C2 2 H3 2 Cl2 Cu2 N6O14 ,晶体学参数a =1 0 81 2 0 ( 3 )nm ,b=2 .5 71 87( 7)nm ,c=1 1 777( 3 )nm ,β=1 0 4 1 472( 5 )°,V =3 1 75 7( 2 )nm3 ,Z =4,Dc=1 679Mg/m3 ,F( 0 0 0 ) =1 640 ,μ(MoKα) =1 5 82mm-1,R =0 0 3 5 8,Rw=0 1 0 0 7。2个铜 (Ⅱ )原子 ,一个呈畸变的NO3 平面体正方形配位构型 ,一个具有畸变的N2 O3 四角锥配位构型 ,晶体内每 2个分子通过分子间氢键作用形成缔合分子对。红外光谱表明 ,配体在形成配合物后 ,ν(CO)和ν(CN )红移。电子光谱表明 ,存在d d 和π π 跃迁。荧光光谱表明 ,配合物金属对配体n π 激发 ( 3 1 0nm)引起的发射峰有较大的影响。