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1.
The equilibrium geometries, relative stabilities, and electronic properties of MnAgm(M=Na, Li; n + m ≤ 7) as well as pure Agn, Nan, Lin (n ≤ 7) clusters are systematically investigated by means of the density functional theory. The optimized geometries reveal that for 2 ≤ n ≤ 7, there are significant similarities in geometry among pure Agn, Nan, and Lin clusters, and the transitions from planar to three-dimensional configurations occur at n = 7, 7, and 6, respectively. In contrast, the first three-dimensional (3D) structures are observed at n + m = 5 for both NanAgm and LinAgm clusters. When n + m ≥5, a striking feature is that the trigonal bipyramid becomes the main subunit of LinAgm. Furthermore, dramatic odd-even alternative behaviours are obtained in the fragmentation energies, secondorder difference energies, highest occupied and lowest unoccupied molecular orbital energy gaps, and chemical hardness for both pure and doped clusters. The analytic results exhibit that clusters with an even electronic configuration (2, 4, 6) possess the weakest chemical reactivity and more enhanced stability.  相似文献   

2.
The equilibrium geometries,relative stabilities,and electronic properties of Mn Agm(M=Na,Li;n + m ≤ 7) as well as pure Ag n,Na n,Li n(n ≤ 7) clusters are systematically investigated by means of the density functional theory.The optimized geometries reveal that for 2 ≤ n ≤ 7,there are significant similarities in geometry among pure Ag n,Na n,and Li n clusters,and the transitions from planar to three-dimensional configurations occur at n = 7,7,and 6,respectively.In contrast,the first three-dimensional(3D) structures are observed at n + m = 5 for both Na n Ag m and Li n Ag m clusters.When n + m ≥ 5,a striking feature is that the trigonal bipyramid becomes the main subunit of Li n Ag m.Furthermore,dramatic odd-even alternative behaviours are obtained in the fragmentation energies,secondorder difference energies,highest occupied and lowest unoccupied molecular orbital energy gaps,and chemical hardness for both pure and doped clusters.The analytic results exhibit that clusters with an even electronic configuration(2,4,6) possess the weakest chemical reactivity and more enhanced stability.  相似文献   

3.
汤沛哲  刘海涛  朱洁  王山鹰  段文晖 《中国物理 B》2012,21(2):27104-027104
The structural and magnetic properties of Fen-mGam (n=3~6, m=0~2; n=13, m=0~3) alloy clusters have been studied using density functional theory. The substitutional doping is favourable for small clusters with up to six atoms at low Ga concentration and substitutional Ga atoms in 13-atom clusters prefer surface sites. The Ga-doping generally could reduce the energetic stability but enhance the electronic stability of Fe clusters, along with a decrease of the local magnetic moments of Fe atoms around Ga dopants. These findings provide a microscopic insight into Fe-Ga alloys which are well-known magnetostriction materials.  相似文献   

4.
Orbital responses to methyl sites in CnH2n+2 (n=1-6) are studied by B3LYP/TZVP based on the most stable geometries using the B3LYP/aug-cc-pVTZ method. Vertical ionization energies are produced using the SAOP/et-pVQZ model for the complete valence space. The highest occupied molecular orbital (HOMO) investigations indicate the p-electron profiles in methane, ethane, propane, and n-butane. By increasing the number of carbon-carbon bonds in lower momentum regions, the s, p-hybridized orbitals are built and display strong exchange and correlation interactions in lower momentum space (P≤0.50 a.u.). Meanwhile, the relative intensities of the isomers in lower momentum space show the strong bonding number dependence of the carbon-carbon bonds, meaning that more electrons have contributed to orbital construction. The study of representative valence orbital momentum distribution further confirms that the structural changes lead to evident electronic rearrangement over the whole valence space. An analysis based on the isomers reveals that the valence orbitals are isomer-dependent and the valence ionization energy experiences an apparent shift in the inner valence space. However, such shifts are greatly reduced in the outer valence space. Meanwhile, the opposite energy shift trend is found in the intermediate valence space.  相似文献   

5.
张金平  程新路  张红  杨向东 《中国物理 B》2011,20(6):60401-060401
Three low-lying electronic states (x1+,a3+,and A1) of NO+ ion are studied using the complete active space self-consistent-field (CASSCF) method followed by highly accurate valence internally contracted multi-reference configuration interaction (MRCI) approach in combination of the correlation-consistent sextuple basis set augmented with diffuse functions, aug-cc-pV6Z. The potential energy curves (PECs) of the NO+(x1+,a3+,A1) are calculated. Based on the PECs, the spectroscopic parameters Re, De, ωe, ωeχe, α e, Be, and D0 are reproduced, which are in excellent agreement with the available measurements. By numerically solving the radial Schrödinger equation of nuclear motion using the Numerov method, the first 20 vibrational levels, inertial rotation and centrifugal distortion constants of NO+(x1+,a3+,A1) ion are derived when the rotational quantum number J is equal to zero (J = 0) for the first time, which accord well with the available measurements. Finally, the analytical potential energy functions of these states are fitted, which are used to accurately derive the first 20 classical turning points when J = 0. These results are compared in detail with those of previous investigations reported in the literature.  相似文献   

6.
王杰敏  冯恒强  孙金锋  施德恒 《中国物理 B》2012,21(2):23102-023102
The potential energy curves (PECs) of three low-lying electronic states (X1Σg+, w3Δu, and W1Δu)of P2 molecule are investigated using the full valence complete active space self-consistent field (CASSCF) method followed by the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in conjunction with the correlation-consistent basis set in the valence range. The PECs of the electronic states involved are modified by the Davidson correction and extrapolated to the complete basis set (CBS) limit. With these PECs, the spectroscopic parameters of the three electronic states are determined and compared in detail with the experimental data. The comparison shows that excellent agreement exists between the present results and the available experimental data. The complete vibrational states are computed for the w3Δu, and W1Δu electronic states when the rotational quantum number J equals zero and the vibrational level G(v), the inertial rotation constant Bv, and the centrifugal distortion constant Dv of the first 30 vibrational states are reported, which accord well with the experimental data. The present results show that the two-point extrapolation scheme can obviously improve the quality of spectroscopic parameters and molecular constants.  相似文献   

7.
Ag3PO4/Ag/Ag2Mo2O7 composite photocatalyst was successfully prepared via an in situ precipitation method. The as-prepared Ag3PO4/Ag/Ag2Mo2O7 nanocomposite included Ag3PO4 nanoparticles (NPs) as well as Ag NPs assembling on the surface of Ag2Mo2O7 nanowires. Under visible light irradiation (λ>420 nm), the Ag3PO4/Ag/Ag2Mo2O7 composite degraded rhodamine B (Rh B) efficiently and showed much higher photocatalytic efficiency than pure Ag3PO4, Ag2Mo2O7, or Ag3PO4/Ag2Mo2O7. It was elucidated that the excellent photocatalytic performance of Ag3PO4/Ag/Ag2Mo2O7 for the degradation of Rh B under visible light could be ascribed to the high specific surface area, the extended absorption in the visible light region resulting from the Ag3PO4/Ag loading, and the efficient separation of photogenerated electrons and holes through the ternary heterostrucure composed of Ag3PO4, Ag and Ag2Mo2O7.  相似文献   

8.
We define a general procedure, based on analyticity and dispersion relations, to estimate low-energy amplitudes for processes like: φe + e - M and φγM, starting from cross-section data on e + e -φM, where M is a generic light scalar or pseudoscalar meson. In particular this procedure is constructed to obtain predictions on the radiative decay rate which are crucially linked on the assumed quark structure for the meson M under consideration. Three cases are analyzed: M = η, M = f 0(qˉ) and M = f 0(qqˉ). While in the η case the estimate of the branching fraction for the radiative decay φηγ is in agreement with the data, in the case of f 0, such agreement is obtained only under the hypothesis of a tetraquark scalar meson.  相似文献   

9.
In this work, the hydrogen storage properties of the Mg-based hydrides, i.e., Mg1-xMxH2 (M=Ti, V, Fe, 0 ≤ x ≤ 0.1), are studied using the Korringa-Kohn-Rostoker (KKR) calculation with the coherent potential approximation (CPA) approximation. In particular, the nature and the concentrations of the alloying elements and their effects are studied. Moreover, the material's stability and hydrogen storage thermodynamic properties are discussed. In particular, we find that the stability and the temperature of desorption decrease without significantly affecting the storage capacities.  相似文献   

10.
杨国  张国营  高娇  薛刘萍  夏天  张学龙 《中国物理 B》2011,20(1):17802-017802
The superexchange interaction on a magnetic ion may be represented by an effective field Hm = λM in some paramagnetic materials, here λ is the coefficient of effective field and M = χHe with χ being the magnetic susceptibility and He being the applied field. The variation of the equivalent λχ with the dynamic applied field is given and the crystal field-splitting levels of the excited configuration 4f75d1 of the Tb3+ ion are calculated in the Tb3Ga5O12. By means of the effective field Hm and the applied field He, the Faraday rotation of Tb3Ga5O12 at 6 K and 41 K, under the high magnetic field and at 0.63 μm wavelength, are presented. Our calculated results are in agreement with the experimental data.  相似文献   

11.
丁利苹  邝小渝  邵鹏  赵亚儒  李艳芳 《中国物理 B》2012,21(4):43601-043601
Using the meta-generalized gradient approximation (meta-GGA) exchange correlation TPSS functional, the geo- metric structures, the relative stabilities, and the electronic properties of bimetallic Ag n X (X=Au, Cu; n=1–8) clusters are systematically investigated and compared with those of pure silver clusters. The optimized structures show that the transition point from preferentially planar to three-dimensional structure occurs at n = 6 for the Ag n Au clusters, and at n = 5 for Ag n Cu clusters. For different-sized Ag n X clusters, one X (X=Au or Cu) atom substituted Ag n+1 structure is a dominant growth pattern. The calculated fragmentation energies, second-order differences in energies, and the highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) energy gaps show interesting odd–even oscillation behaviours, indicating that Ag 2,4,6,8 and Ag 1,3,5,7 X (X=Au, Cu) clusters keep high stabilities in comparison with their neighbouring clusters. The natural population analysis reveals that the charges transfer from the Ag n host to the impurity atom except for the Ag 2 Cu cluster. Moreover, vertical ionization potential (VIP), vertical electronic affinity (VEA), and chemical hardness (η) are discussed and compared in depth. The same odd–even oscillations are found for the VIP and η of the Ag n X (X=Au, Cu; n=1–8) clusters.  相似文献   

12.
刘小勇  朱正和  盛勇 《中国物理 B》2011,20(11):113101-113101
Employing the density functional theory, we investigate the lowest-energy geometric, the stable and the electronic properties of Agn-1Y (n=2-10) clusters in this paper. The structural optimization and the frequency analysis are performed at the B3LYP/LANL2DZ level. Meanwhile, the differences in geometry, stability and electronic properties between Agn and Agn-1Y (n=2-10) clusters are also studied. The results show that for the doping of the yttrium atoms, the structures and the average binding lengths of the Agn clusters are greatly changed. In addition, the thermodynamic stabilities of the Agn clusters are enhanced generally with the doping of the Y atoms. In addition, the chemical stabilities of the Agn-1Y clusters are still improved compared with that of the three-dimensional Agn clusters.  相似文献   

13.
张秀荣  李扬  尹琳  王杨杨 《物理学报》2013,62(2):23601-023601
采用密度泛函理论(DFT)中的B3LYP方法,在LANL2DZ基组水平上对WnNim(n+m=8)团簇的各种可能构型进行了几何参数全优化,得到了它们的基态构型;并对基态构型的偶极距、极化率、红外光谱和拉曼光谱性质进行了分析,结果表明:团簇WnNim(n+m=8)都具有极性,富W团簇非线性光学效应强,容易被外加场极化;振动频率主要分布在0-350 cm-1范围内,团簇W4Ni4因其振动方式的特殊性,红外光谱和拉曼光谱在频率421.971 cm-1处,都有明显强峰;团簇W5Ni3因其结构的高对称性在振动光谱中出现多处共振现象.  相似文献   

14.
李兵  杨传路  齐凯天  张岩  盛勇 《物理学报》2009,58(5):3104-3111
使用密度泛函理论(DFT)的杂化密度泛函B3LYP方法在6-31G*基组水平上对SimCnm+n≤7)团簇各种可能的构型进行几何结构优化,预测了各团簇的最稳定结构. 并对最稳定结构的平均结合能(Eb),二阶能量差分(Δ2E)和能隙(Eg)等进行了理论研究. 结果表明,随着原子个数的增加,SiC二元团 关键词mCnm+n≤7)团簇')" href="#">SimCnm+n≤7)团簇 密度泛函理论 结构与性质  相似文献   

15.
葛桂贤  井群  曹海宾  杨增强  唐光辉  闫红霞 《物理学报》2011,60(10):103102-103102
采用密度泛函理论中的广义梯度近似(GGA) 对 Run Au和Run 团簇的几何构型进行优化,并对能量、频率、电子性质和磁性质进行了计算. 结果表明,Run Au团簇的最低能量结构可以通过Au原子代替Run+1团簇中的Ru原子生长而成.除了局域的结构畸变,Run Au和Run+1团簇具有相似的几何结构.二阶能量差分、电离势、亲和势和分裂能表明Ru5, Ru8, Ru5Au, Ru8Au 是稳定的团簇,Au的掺杂没有改变Run 的相对稳定性.通过电子性质的分析发现,当Au原子掺杂在Run 中,团簇的化学活性增加,且团簇的能隙主要由电子的配对效应决定;对于大多数团簇来说,Au原子掺杂提高了Run Au的磁矩. 关键词: n Au和Run 团簇')" href="#">Run Au和Run 团簇 几何结构 电子性质  相似文献   

16.
采用二项式方案构建了FenOm+(n+m=4)团簇的大量可能初始结构.运用广义梯度近似(GGA)密度泛函理论中的PW91交换关联泛函对这些初始结构进行优化和频率分析,得到12个稳定的异构体.在此基础上计算和分析了它们的结合能、对称性、键长、磁矩,最高占据轨道与最低未占据轨道的能隙.发现Fe—O键在FenOm+(n+m=4)团簇的稳定中具有重要作用,团簇的总磁矩主要取决于铁原子的磁矩和各个原子磁矩排布情况.  相似文献   

17.
The structural, electronic and magnetic properties of small gallium clusters doped with Cobalt have been studied using spin-polarised density functional theory. The binding energy per atom, second-order differences of total energies and fragmentation energies of equilibrium geometries of the host Gan+1 and doped GanCo (n = 1–12) clusters are computed. Doped clusters are found to be more stable than pure Ga clusters; Ga3Co, Ga5Co and Ga8Co clusters are exceptionally stable. Doping with Co changes the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO–LUMO) gap, and also affects the magnetic moments of clusters.  相似文献   

18.
李晶  刘小勇  朱正和  盛勇 《中国物理 B》2012,21(3):33101-033101
The geometries of MgnNi2 (n=1-6) clusters are studied by using the hybrid density functional theory (B3LYP) with LANL2DZ basis sets. For the ground-state structures of MgnNi2 clusters, the stabilities and the electronic properties are investigated. The results show that the groundstate structures and symmetries of Mg clusters change greatly due to the Ni atoms. The average binding energies have a growing tendency while the energy gaps have a declining tendency. In addition, the ionization energies exhibit an odd-even oscillation feature. We also conclude that n=3, 5 are the magic numbers of the MgnNi2 clusters. The Mg3 Ni2 and Mg5Ni2 clusters are more stable than neighbouring clusters, and the Mg4Ni2 cluster exhibits a higher chemical activity.  相似文献   

19.
金蓉  谌晓洪 《物理学报》2010,59(10):6955-6962
用B3LYP/LANL2DZ方法对ZrnPd(n =1—13)团簇的平衡几何结构、能量、频率、电子性质和磁性进行了计算.研究表明,Pd原子位于表面的异构体更为稳定,其中Zr7Pd,Zr12Pd团簇稳定性高,是幻数团簇,此外,相对于ZrnCo与ZrnFe团簇,ZrnPd团簇参与化学反应的能力较弱,化学稳定性更  相似文献   

20.
陈冬冬  邝小渝  赵亚儒  邵鹏  李艳芳 《中国物理 B》2011,20(6):63601-063601
We have systematically investigated the geometrical structures, relative stabilities and electronic properties of small bimetallic AunBe (n = 1, 2, . . . , 8) clusters using a density functional method at BP86 level. The optimized geometries reveal that the impurity beryllium atom dramatically affects the structures of the Aun clusters. The averaged binding energies, fragmentation energies, second-order difference of energies, the highest occupied-lowest unoccupied molecular orbital energy gaps and chemical hardness are investigated. All of them exhibit a pronounced odd-even alternation, manifesting that the clusters with even number of gold atoms possess relatively higher stabilities. Especially, the linear Au2Be cluster is magic cluster with the most stable chemical stability. According to the natural population analysis, it is found that charge-transferring direction between Au atom and Be atom changes at the size of n = 4.  相似文献   

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