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TiC、TiC1-x、(Ti1-xNbx)C电子结构的计算 总被引:2,自引:0,他引:2
采用离散变分x_α法(DV-X_α法)对TiC理想晶体、空位和掺杂缺陷结构中的电子结构进行了计算.通过选取分子簇模型,模拟了理想晶体、空位和掺杂缺陷情况.采用多重散射离散变分X_α法,通过自治迭代来求解局域密度泛函方程,得到了各个分子簇模型的电子结构.分析计算结果发现,在理想TiC结构的态密度图中,费米能级位于两峰之间.但在费米能级处的电子态密度不为零,这提供了TiC导电性的来源.在空位模型中,发现电子态密度在费米能级处有较大的值,说明空位的存在有利于提高TiC的导电能力.对于Nb掺杂后的电子结构,在费米能级处存在一个电子态密度峰,因而也有利于提高其导电性.在计算的过程中考虑到了分子簇模型边界条件带来的电行转移效应对电子结构的影响,通过提供适当的环境势,得到了较精确的计算结果.与已有的计算结果进行了对比,有较好的一致性. 相似文献
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采用半经验的AM1法,对环状聚茚并茚及其取代物的电子结构进行了计算研究 ,探讨了其磁性和取代基效应.计算得到,环状聚茚并茚及其取代物皆表现半导体 性质且发现其中一种异构体可能具有磁性.取代基效应表明,吸电子基团的取代使 聚合物的电子亲合势增大,而给电子基团的取代则导致电离势减少,但取代基效应 不能改变聚合物的半导体性质.此外,无论吸电子基团还是给电子基团的取代都不 能改变聚合物的磁性特征. 相似文献
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自从1990年用电弧法成功地制备出宏观量的C60和C70以来,富勒烯的电化学研究有了迅速的发展.理论研究指出,在一个C60簇化合物中,有六个吡喃环烯单元,可分别得到一个电子使五元环芳香化,从而形成C(n=1~6)阴离子.Haufler首先报导了C60可逆的两步单电子还原,之后一些作者陆续得到了三步、四步和五步单电子电还原过程.直到达1992年,在使用混合溶剂并控制低温-10℃至5℃和-88℃至60℃条件下,才得到了C60的六步电还原伏安图.富勒烯的微电极伏安法的研究极少见报导.杨汉西等用铂微电极得到了C60三步电还原的稳态伏安图.本文在… 相似文献
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3’-大豆甙元磺酸钠的电化学行为及应用研究 总被引:27,自引:2,他引:27
采用线性扫描伏安法、循环伏安法和常规脉冲伏安法电化学手段详细研究了改 性药物3’-大豆甙元磺酸钠(3’-daidzein sulfonic sodium,Dss)在pHl.0—6. 2的水溶液中的电化学行为.在不同pH范围内得到了Das的三个还原波.研究证实, 在pH<3.2条件下所获得的Pcl,Pc2波分别为质子化的Dss的单电子不可逆吸附还 原波及还原中间体自由基的单电子单质子不可逆吸附还原波;在3.2<pH<6.2条 件下所获得的Pc3波,属于Dss后随质子化的单电子不可逆吸附还原波,而还原中间 体自由基的单电子波被氢波掩盖.测得在单分子层饱和吸附的条件下,每一个Dss 分子所占汞电极面积为0.664nm^2.此外,通过邻苯三酚自氧化产生活性氧自由基再 还原,对Dss清除活性氧自由基能力进行了研究,从电化学角度对其药理机制进行 了探讨,研究证实Dss具有较强的抗氧化性,是一种有效的活性氧自由基清除剂. 相似文献
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准一维聚并苯体系是一类典型的梯形结构有机导体材料.采用量子化学一维紧束缚自洽场晶体轨道CNDO/2 方法,研究了顺、反式聚并苯和取代聚并苯的结构、能量和电子布居.计算了甲基、甲氧基、氯和羟基取代聚并苯的电子能带,与聚并苯进行了分析比较.结果表明:(1)单取代使对称性明显降低,对聚并苯的能带结构影响较大,使能隙值普遍增大,导电性能降低.(2)双取代虽使电荷重新分布,但基本保持聚并苯自身结构特征.取代聚并苯与聚并苯比较能隙值变化不大.对于不同的取代基影响规律不同.对位双取代与间位双取代也表现出差异.(3)顺式和反式结构聚并苯的电子性质略有差异,取代后变化较大. 相似文献
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The structural and electronic properties of perfluorinated surfactants perfluorooctane sulfonate (PFOS) and lithium perfluorooctane sulfonate (LiPFOS) have been investigated theoretically by performing semi-empirical molecular orbital theory at the level of AM1 calculations. The optimized structure and the electronic properties of the molecules are obtained. 相似文献
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1-异丙基环己硅烷类液晶化合物的量子化学研究--取代联苯基乙烷系列 总被引:1,自引:0,他引:1
我们曾用半经验的分子轨道方法对标题化合物的某些系列进行过计算[1 ,2 ] 。本文选择 7种 1 异丙基环己硅烷 取代联苯基乙烷系列化合物 ,以SCF—MO—AM1 [3] 和PM3[4] 两种方法 ,优化出它们稳定的几何构型 (分子的总能量最低、核—核排斥能最小 )并对其作了振动分析 ;同时计算了标题物在该稳定构型下的电子结构和若干基本性质。1 计算图 1示出了 7种标题化合物的结构及原子编号。用MOPAC7.0程序中的AM1 和PM3方法 ,分子的初始构型参数采用Pople’s标准构型数据[5] 。对每个分子实行能量梯度全优化和SCF计算。… 相似文献
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Vadali RV Shi Y Kumar S Kale LV Tuckerman ME Martyna GJ 《Journal of computational chemistry》2004,25(16):2006-2022
Many systems of great importance in material science, chemistry, solid-state physics, and biophysics require forces generated from an electronic structure calculation, as opposed to an empirically derived force law to describe their properties adequately. The use of such forces as input to Newton's equations of motion forms the basis of the ab initio molecular dynamics method, which is able to treat the dynamics of chemical bond-breaking and -forming events. However, a very large number of electronic structure calculations must be performed to compute an ab initio molecular dynamics trajectory, making the efficiency as well as the accuracy of the electronic structure representation critical issues. One efficient and accurate electronic structure method is the generalized gradient approximation to the Kohn-Sham density functional theory implemented using a plane-wave basis set and atomic pseudopotentials. The marriage of the gradient-corrected density functional approach with molecular dynamics, as pioneered by Car and Parrinello (R. Car and M. Parrinello, Phys Rev Lett 1985, 55, 2471), has been demonstrated to be capable of elucidating the atomic scale structure and dynamics underlying many complex systems at finite temperature. However, despite the relative efficiency of this approach, it has not been possible to obtain parallel scaling of the technique beyond several hundred processors on moderately sized systems using standard approaches. Consequently, the time scales that can be accessed and the degree of phase space sampling are severely limited. To take advantage of next generation computer platforms with thousands of processors such as IBM's BlueGene, a novel scalable parallelization strategy for Car-Parrinello molecular dynamics is developed using the concept of processor virtualization as embodied by the Charm++ parallel programming system. Charm++ allows the diverse elements of a Car-Parrinello molecular dynamics calculation to be interleaved with low latency such that unprecedented scaling is achieved. As a benchmark, a system of 32 water molecules, a common system size employed in the study of the aqueous solvation and chemistry of small molecules, is shown to scale on more than 1500 processors, which is impossible to achieve using standard approaches. This degree of parallel scaling is expected to open new opportunities for scientific inquiry. 相似文献
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The effect of confinement on the electronic energy and polarizability of a hydrogen molecular ion 下载免费PDF全文
Josimar Fernando da Silva Fabrício Ramos Silva Elso Drigo Filho 《International journal of quantum chemistry》2016,116(7):497-503
The electronic energy and the polarizability of a confined hydrogen molecular ion in the ground state and the first excited state, for cavities of different volumes, are calculated using the variational method. In the treatment adopted an alternative molecular wave function is introduced with only one variational parameter and based on wave functions used for confined atoms. © 2016 Wiley Periodicals, Inc. 相似文献
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Triplet-triplet energy transfer in fluorene dimer is investigated by combining rate theories with electronic structure calculations. The two key parameters for the control of energy transfer, electronic coupling and reorganization energy, are calculated based on the diabatic states constructed by the constrained density functional theory. The fluctuation of the electronic coupling is further revealed by molecular dynamics simulation. Succeedingly, the diagonal and off-diagonal fluctuations of the Hamiltonian are mapped from the correlation functions of those parameters, and the rate is then estimated both from the perturbationtheory and wavepacket diffusion method. The results manifest that both the static and dynamic fluctuations enhance the rate significantly, but the rate from the dynamic fluctuation is smaller than that from the static fluctuation. 相似文献
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Shen Haijun 《化学物理学报(中文版)》2004,17(6):717-721
The geometry,electronic structure and electronic transmission of Au electrode-compressed C20 fullerene Au electrode systems are investigated systemically,and some interesting results are obtained by use of molecular dynamics,Extend Hückel method of the first principle,and Green's function based method. The analytical results show that,due to intervention of Au electrodes,the electronic structure of compressed C20 fullerene is changed significantly,the coalescent between C20 fullerene and Au electrodes is intervenient of covalent bond and electrovalent bond,and the compressed C20 fullerenes are better conductors of electricity than those uncompressed or slightly compressed ones. The methods and the relative conclusions are beneficial to go further deep into electronic transmission of carbon fullerenes. 相似文献