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活体23Na NMR及在生物医学中的应用   总被引:1,自引:0,他引:1  
胞内Na+浓度和跨膜梯度的维系对于保持组织细胞的正常生理状态具有重要的作用.本文详细介绍了生物组织细胞内Na+测定的23Na NMR方法,并讨论了23Na NMR在生理病理学研究和疾病诊断等生物医学领域内的应用。  相似文献   

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以含时密度泛函理论为基础,结合从头赝势方法运用含时局域密度近似计算了Na5,Na6和Na7团簇的动力学极化强度,并通过傅里叶变换得出了团簇的光学吸收谱.研究表明,计算结果可以较好地再现实验谱,而且Na6和Na7团簇的结果和组态相互作用的结果符合较好.二维结构和三维结构的Na6团簇的计算结果表明,只有二维结构可出现低于2 eV以下的峰,而且二维结构光谱的计算结果与实验结果符合较好.  相似文献   

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有限温度下Na4团簇的异构化   总被引:2,自引:2,他引:0  
在紧密结合分子动力学模型基础上,对Na4的两种异构体D2h和C2V和结构性质随温度的进行了系统性研究。发现在低温时,这两划构体具有明显有不同;在较高温度时,能够发现C2V和D2h两种异构体之间的转变;在更高温度时,这两种异构体C2v和D2h都处于液态。  相似文献   

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运用距离相关紧密结合的分子动力学模型。对金属原子团簇Na8的两种不同的异构体进行了数值模拟.根据零温下基态结构中不同原子到质心的不同距离,把Na8的两种异构体分为多个子系统.分别提取各个子系统在不同温度下的围绕质心的径向分布、无单位键长涨落、平均位移、扩散系数。发现尽管两个异构体的基态能量很接近。但他们的稳定性、熔化过程的热力学性质等有着很大的差别,这也反映了它们在几何结构上的差别.  相似文献   

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硷二聚物与氧反应碰撞的中间络合物是M~ _2X~-离子对(M代表硷原子,X代表氧原子或氧分子)。我们导出了Na~ _2O~-和Na~ _2O~-_2体系最低能量电子态绝热势能面的解析形式。  相似文献   

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类Na铜离子软X射线激光初步研究   总被引:1,自引:0,他引:1  
张正泉  范品忠 《光学学报》1991,11(3):93-197
本文报道在上海光机所LF12~#激光装置上利用自制极紫外掠入射光栅摄谱仪,进行类Na铜离子复合泵浦软X射线激光研究的初步实验结果,低泵浦条件下(2.5×10~(12)W/cm~2)的光谱表明,得到自发发射放大是有希望的。文章还给出了类Na等电子数序列离子复合激光波长与原子序数的关系及推广到水窗波段的可能性。  相似文献   

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采用距离相关的紧密结合模型,对Nan(n=2-5)的振动特性进行了分析。通过求解Hessian矩阵和对距离相关的紧密结合分子动力学轨道所作的速度自关联函数的福里叶变换分析,得到了这些钠原子微团簇的振动频率。对Na2和Na3,这两种计算方法和实验,和从头计算法的计算结果一致,并对Na4和Na5的振动频率作了预言。  相似文献   

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The static electric dipole polarizability of Na N clusters with even N has been calculated in a collective, axially averaged and a three-dimensional, finite-field approach for , including the ionic structure of the clusters. The validity of a collective model for the static response of small systems is demonstrated. Our density functional calculations verify the trends and fine structure seen in a recent experiment. A pseudopotential that reproduces the experimental bulk bond length and atomic energy levels leads to a substantial increase in the calculated polarizabilities, in better agreement with experiment. We relate remaining differences in the magnitude of the theoretical and experimental polarizabilities to the finite temperature present in the experiments. Received 8 November 1999  相似文献   

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The magnetic properties, electronic structure, and optical properties of the filled skutterudite BaFe4Sb12 are calculated by the first-principles full-potential linearized augmented plane wave (FPLAPW) plus local orbital method. It is found that the local spin density approximation (LSDA) method appears more accurate than the generalized gradient approximation (GGA) method in calculating the electronic structures and optical properties of this compound. Furthermore, our calculated lattice constant and spin magnetic moments with the LSDA method are in overall better agreement with experiment. In contrast with recent experiment, our calculations are in good agreement with experimental reflectivity spectra and optical conductivity spectrum.  相似文献   

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The systematics of the plasmon response in spherical K, Na and Li clusters in a wide size region is studied. Two simplifying approximations whose validity has been established previously are considered: (a) a separable approach to the random-phase-approximation, involving an expansion of the residual interaction into a sum of separable terms, (b) the electron-ion interaction is modeled within the pseudo-Hamiltonian jellium model (PHJM) including nonlocal effects by means of realistic atomic pseudoHamiltonians. In cases where nonlocal effects turn out to be negligible, the Structure Averaged Jellium Model (SAJM) has been used. The leading role of Landau damping in forming the plasmon width in medium and large clusters is demonstrated. Good agreement with available experimental data is achieved for K, Na (using the SAJM) and small Li clusters (invoking the PHJM). The trends for peak position and width are generally well reproduced, even up to details of the Landau fragmentation in several clusters. Less good agreement, however, is found for large Li clusters. The possible reasons of the discrepancy are discussed. Received: 22 April 1998 / Accepted: 24 July 1998  相似文献   

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Na5Er(WO4)4晶体的光谱参数   总被引:1,自引:0,他引:1  
郭常新  林泳 《发光学报》1993,14(2):197-199
Na5Er(WO4)4是化学计量的基质发光晶体,含有很高浓度的Er,它的发光却没有明显的浓度猝灭.与Na5Er(WO4)4结构相同的Na5Nd(WO4)4单晶是良好的激光材料,已获得激光输出.而Er3+在YAlO3,Y3Al5O12和CaF2中也实现了激光输出[1],在ErP5O14[1],Y3Al5O12:Er3+[2]和掺Er3+磷酸盐玻璃[3]的光学参数和某些谱线出激光的可能性已有研究.  相似文献   

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Wenqiang Ma 《光谱学快报》2014,47(10):754-760
The present paper describes the studies on the adsorption behavior and charge transfer from isonicotinic acid to silver nanoparticles with experiment and theory. Compared with UV–Visible adsorption spectrum, the adsorption spectrum of Ih-Ag13 cluster was quite good agreed with that of silver colloidal nanoparticle. So that one Ag13 cluster as a substrate was used to simulate Raman frequencies of the adsorption configuration. Here, it is demonstrated the calculated Raman spectra are in good agreement with experimental results. The analysis of Mulliken charge was obtained by density functional theory, which indicated the charge characteristics of Ag13 nanoparticle. Once isonicotinic acid molecules were adsorbed on sliver clusters, the charges transfer from isonicotinic acid to silver clusters, so that the surface charges of silver clusters are uneven.  相似文献   

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The orientation dependences of the second-order quadrupole shifts of the central component in the 23Na NMR spectrum were studied in the temperature range 293–760 K. The profile of the spectral distribution is calculated using various models of the Na1/2Bi1/2TiO3 structure. The calculations agree with the experimental data for the monoclinic structure of a polar cluster with two Na displacement components: a displacement along the [111] p direction and a small displacement statistically or dynamically disordered over six equally probable [100] p -type directions. Tetragonal-phase nuclei and monoclinic clusters with a very small displacement component along the [111] p direction are found to coexist and have close energies over the temperature range 580–610 K. The results obtained provide new information concerning the character of the diffuse phase transition at 610 K.  相似文献   

18.
Density functional calculations have been carried out to obtain low energy equilibrium geometries of anionic and neutral sodium clusters over a wide range of sizes 40 ≤ N ≤ 147, where N is the number of atoms. An exhaustive search for the low energy equilibrium geometries has been carried out. The density of states of the lowest energy geometries are compared with the experimental photoelectron spectra (Huber et al 2009 Phys. Rev. B 80 235425; Kostko et al 2007 Phys. Rev. Lett.98 043401) for N > 41. The agreement between theory and experiment is good for almost all the clusters and the changes in the spectrum with size correlate very well with the changes in the shapes as observed in the evolutionary trend of the ground state geometries.  相似文献   

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We use time-dependent density functional theory coupled to molecular dynamics for ionic motion to compute the spectra of ionic vibrations in small Na clusters. Comparison with results from the distance dependent tight-binding approach shows good agreement between these two very different methods. We discuss the evolution of the spectra with cluster size and charge and the impact of ionic vibrations on the optical response. Received 23 July 2001 / Received in final form 5 July 2002 Published online 8 October 2002 RID="a" ID="a"e-mail: suraud@irsamc.ups-tlse.fr  相似文献   

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几何构型不同的Na团簇碰撞动力学研究   总被引:1,自引:0,他引:1       下载免费PDF全文
采用距离相关紧密束缚的分子动力学模型,在不同碰撞能量以及不同的碰撞参数下,研究了两种构型的Na6(2D),Na6(3D)与Na8团簇间的碰撞.讨论了反应机制的变化,即全融合、深度非弹、非弹性碰撞过程.结果表明:构型不同的团簇与相同的靶碰撞显示了不同的特征.低能时Na6(3D)易融合;DIC反应时,易于形成大的团簇 关键词: Na团簇 原子团簇碰撞 紧束缚模型  相似文献   

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