Na5, Na6和Na7团簇光学吸收谱的理论研究

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.     

Na2对超短激光脉冲的响应

应用时间相关的局域密度近似模型研究了Na₂价电子对超短激光脉冲的响应.分别计算了电场极化方向平行和垂直于两原子轴线的情况,结果表明Na₂具有强烈的各向异性 关键词： 团簇 超短脉冲激光 激光与团簇的相互作用     

Ga6N6团簇结构性质的理论计算研究

在密度泛函理论的基础上，对Ga₆N₆团簇进行了第一性原理、全电子、从头计算，得到了10种可能的三维空间结构及其电子结构.其中最稳定结构的一对GaN原子的平均结合能为9.748 eV，因此是可能存在的.但与他人计算的Ga₃N₃和Ga₅N₅相比，Ga₆N₆团簇可能不属于“幻数”团簇.最稳定结构的Ga₆N_{6 关键词： GaN 团簇 电子结构}     

Zr催化剂对NaAlH4和Na3AlH6可逆储氢性能的影响

采用基于密度泛函理论的平面波赝势方法,分别计算纯净的以及掺杂Zr的NaAlH₄和Na₃AlH₆的晶格结构常数、能量、电子局域函数和电子态密度.结果表明：NaAlH₄和Na₃AlH₆分别是带隙为46和31 eV的绝缘体;NaAlH₄和Na₃AlH₆中Al—H键是共价键,Na—H键是离子键;Zr原子替代Na原子 关键词： 储氢 4')" href="#">NaAlH₄ 3AlH₆')" href="#">Na₃AlH₆ Zr掺杂     

Na3的电子结构与构形

应用离散变分方法，计算了Na₃的基态势能面，并由此得到平衡构形参数、振动频率、Jahn-Teler稳定能、Jahn-Teler局域能等，所得结果与实验符合得较好 关键词：     

H2在Al7-团簇解离吸附的理论研究

利用高精度从头计算方法研究了H₂分子在Al₇^-阴离子团簇上的吸附及解离过程, 确定了分子吸附及解离吸附的稳定结构,并分析了各结构的光电子能谱. 计算表明H₂在Al₇^-上为弱的物理吸附,吸附能约为0.02 eV;解离过程的能垒约为0.75 eV. 对团簇及解离吸附结构的态密度与实验得到的光电子能谱的比较表明二者能够很好地符合, 确定H₂与激光烧蚀产生的团簇直接反应时能在Al₇^-上发生解离. 关键词： 7^-')" href="#">Al₇^- 2')" href="#">H₂ 解离吸附 从头计算     

GanN－m阴离子团簇的结构及稳定性的研究

利用密度泛函理论(DFT)对Ga_nN^-(n=2—8)和Ga_nN^-₂ (n=1—7)阴离子团簇的结构及稳定性进行了研究.在B3LYP/6-31G^*水平上进行了结构优化和频率分析，得到了Ga_nN^-(n=2—8)和Ga_nN^-₂(n=1—7)阴离子团簇的基态结构.在这些团簇中，原子总数小于等于6的团簇的几何结构为平面结构，原子总数大于6的团簇的几何结构为立体结构；在所研究的团簇中，Ga₄N^-，Ga₆N^-,Ga₄N^-₂和Ga₅N^-₂的基态结构较稳定. 关键词： nN^-_m团簇')" href="#">Ga_nN^-_m团簇 密度泛函理论(DFT) 几何结构     

二维全同Nb4团簇在Cu(100)表面的结构稳定性和电子性质

使用基于密度泛函理论的第一性原理赝势法和超原胞模型，研究了吸附在Cu(100)表面上的二维有序排列的幻数团簇Nb₄的结构稳定性及其电子结构性质.计算表明，四面体结构和平面的菱形结构的Nb₄团簇都可以稳定地吸附在Cu(100)表面上，这个体系很可能有重要的应用前景.在Cu(100)表面上，菱形结构的Nb₄比四面体结构的Nb₄更稳定，从Nb₄团簇的四面体结构到菱形结构，需经过的势垒高度约为0.94eV/团蔟.电子结构的计算表明，在Nb₄吸附后，Cu(100)表面与Nb₄团簇间有明显的电荷重新分布，表面Cu原子的电子态密度也明显改变. 关键词： 4团簇')" href="#">Nb₄团簇 有序排列 结构稳定性 从头计算     

CuSi6团簇几何结构和性质的密度泛函理论研究

利用密度泛函理论（DFT）的B3LYP方法,采用全电子基组6-311+G（d）研究了CuSi₆团簇的几何构型和电子结构性质,计算表明CuSi₆团簇存在多个能量相近的稳定异构体,且结构中存在多个Cu-Si键,多个低能异构体共存解释了实验中观察到的CuSi₆团簇较强的现象.对于CuSi₆团簇,计算得到的三个最稳定异构体的垂直电离能,电子亲和能和HOMO-LUMO能隙均相对较大,也表明这三个异构体较为稳定.     

第一性原理对GanPm小团簇的结构及稳定性的研究

利用密度泛函理论（DFT）对Ga_nP和Ga_nP₂ (n=1—7)团 簇的几何结构、电子态及稳定 性进行了研究. 在B3LYP/6-31G^*水平上进行了结构优化和频率分析，得到了Ga _nP和Ga_nP₂(n=1—7) 团簇的基态结构. 结果表明，n≤ 5团簇的几何结构基本上为平面结构，n ＞ 5的团簇均为立体结构；在Ga_nP₂ (n=1—6)团簇中，P-P比Ga-P容易 成键；在Ga_nP和G a_nP₂ (n=1—7) 团簇中，Ga₃P, Ga₄P, Ga P₂, Ga₂P₂ 和 Ga₄P₂的基态结构最稳定，在所研究的团簇中，稳定性随团簇总原 子数的增大而减小. 关键词： nP_m团簇')" href="#">Ga_nP_m团簇 密度泛函理论（DFT） 几何结构 电子态     

Cun-1Au (n=2–10)团簇结构、静态极化率及吸收光谱的第一性原理研究

采用遗传算法, 得到贵金属混合团簇Cu_n-1Au (n=2–10)的稳态结构, 并采用分别基于静态及含时的密度泛函理论的第一性原理方法计算了团簇的静态极化率和吸收光谱. 由于d电子屏蔽效应的增强, 金原子的引入会导致团簇静态极化率的降低, 但立体的构型能减小这种影响. 基于含时密度泛函理论的第一性原理计算得到的吸收光谱指出, 这种屏蔽效应同时导致共振强度的明显下降. d轨道对跃迁贡献的进一步计算, 指出d轨道成分是团簇的光激发中的主要贡献者, 但d电子的屏蔽作用并不会直接导致在激发中d轨道贡献的提升. 针对固定尺寸体系, Cu_6-nAu_n (n=0–6) 团簇的研究进一步论证了此观点. 计算的光谱与实验值能很好地对应, 并且比其他更早的理论计算更为接近实验值. 关键词： 贵金属混合团簇 静态极化率 B3LYP-TDDFT 吸收光谱     

Ab initio calculations for the absorption spectra and polarizabilities of small sulfur clusters

Absorption spectra for Sn clusters （n=2...8） are calculated using an adiabatic time-dependent density functional formalism within the local density approximation （LDA）. We compare the calculated spectra with those computed using a simple LDA approach. The time-dependent LDA （TDLDA） spectra display a significant blue shift with respect to the LDA spectra. The calculated spectra present a variety of features that can be used for comparison with future experimental investigations. We also obtain a significant threshold absorption, which can distinguish between different ground states of the sulfur clusters. In addition, the polarizabilities of the clusters are calculated by using the higherorder finite-difference pseudopotential density functional method in real space. We find that the polarizabilities of the clusters considered are higher than the value estimated from the ＇hard sphere＇ model using the bulk static dielectric constant. The computed polarizabilities per atom tend to decrease with increasing cluster size. The polarizabilities are closely related to the HOMO-LUMO gaps and the geometrical configurations.     

Study of the electronic structure and spectral features of TiS2,ZrS2 and HfS2 by the Xα discrete variational method

In order to study the electronic structure of TiS₂, ZrS₂ and HfS₂, selfconsistent charge X_α discrete variational calculations of clusters MeS₆^8- (Me = Ti, Zr, Hf) have been performed. The results obtained are consistent with band structure calculations. The covalency of the chemical bonding is shown to increase in the series TiS₂-ZrS₂-HfS₂, which corresponds to the atomization energy in the series. The results are applied in the interpretation of X-ray emission, photoelectron and optical spectra.     

High-order harmonic generation and multi-photon ionization of Na2 in laser fields

In this paper high-order harmonic generation （HHG） spectra and the ionization probabilities of various charge states of small cluster Na2 in the multiphoton regimes are calculated by using time-dependent local density approximation （TDLDA） for one-colour （1064 nm） and two-colour （1064 nm and 532 nm） ultrashort （25 fs） laser pulses. HHG spectra of Na2 have not the large extent of plateaus due to pronounced collective effects of electron dynamics. In addition, the two-colour laser field can result in the breaking of the symmetry and generation of the even order harmonic such as the second order harmonic. The results of ionization probabilities show that a two-colour laser field can increase the ionization probability of higher charge state.     

Electronic structure and the infrared absorption and Raman spectra of the semiconductor clusters C24, B12N12, Si12C12, Zn12O12, and Ga12N12

The optimized configurations, electronic structures, charge transfers, band gaps, total energies, cohesive energies, electron density maps, infrared absorption spectra, Raman spectra, and relevant modes of natural acoustic vibrations for the semiconductor clusters C₂₄, B₁₂N₁₂, Si₁₂C₁₂, Zn₁₂O₁₂, and Ga₁₂N₁₂ are calculated using the ab initio Hartree-Fock method in the 6–31G basis set. Original Russian Text ? V.V. Pokropivny, L.I. Ovsyannikova, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 3, pp. 535–542.     

Static anisotropic and isotropic electric dipole polarizabilities of Na n F n-1 clusters

Recently, electric susceptibilities of Na_nF_n-1 clusters have been measured by deflecting a molecular beam in an inhomogeneous electric field. The analysis of the deflection of a cluster by the electric field needs the calculation of the electric properties. We present the calculation of the static anisotropic and average dipolar polarizabilities within a model in which the Na_nF_n-1 clusters ( 2 n 23) are treated as one electron embedded in the field of n ions Na⁺ and of n - 1 ions F^-. The accuracy of the results is evaluated and discussed on small clusters (n 5) in comparison with ab initio calculations. The relationship between the polarizabilities, the electronic localization and the geometric structure is discussed. Received 10 September 2002 Published online 3 July 2003     

Electronic properties of Bi2O3 and MoO3 and relationships to oxidation catalysis

A semiempirical atom superposition and electron delocalization molecular orbital analysis of the bonding and electronic structure of MoO₃, oxygen deficient MoO₃, and the α, β, and δ phases of Bi₂O₃ has been made. It is found that both small — e.g. MoO₆ — and large — e.g. Mo₆O₂₄ — clusters are useful models for cation electronic structure within the theory used. From the calculations, an interpretation is given for all available optical and photoemission data for the oxides. The color, conductivity, and new photoemission peak of oxygen-deficient MoO₃ conducting bronzes are found to be due to the addition of electrons to the lowest of three Mo 5d bands which are empty in MoO₃. Weakly allowed d ← d transitions in the red are responsible for the color. Strongly allowed Mo 5d ← O 2p charge transfer excitations are responsible for the optical absorption above 3.2 eV. For the bismuth oxides, three occupied bands are found showing strong Bi 6s, 6p, 6d and O 2p hybridization. These bands have been seen experimentally. The highest band surprisingly has Bi 6p lone-pair character which is explained in terms of the relative Bi 6s and 6p and O 2p ionization potentials using perturbation theory. Rather similar electronic structures are found for the three phases despite their varying cation coordinations and structures. A charge transfer optical absorption edge at ～ 2.6 eV for the β form agrees well with observations reported in the literature, and similar edges should occur for the other phases. The cubic δ form has an unusual low-lying band suggesting absorption in the infrared. Our results provide insight into the surface properties of these oxides.     

Vacuum ultraviolet spectroscopy of pure and Ce3+-doped Na0.4Lu0.6F2.2

The spectroscopic properties of wide-band fluoride Na_0.4Lu_0.6F_2.2 crystals activated by Ce³⁺ were investigated. The absorption edge for the matrix was found to be at about 9.5 eV. In the 4- to 8-eV region of the absorption spectrum of Na_0.4Lu_0.6F_2.2: Ce³⁺, all 4f-5d transitions of the Ce³⁺ ion are observed. In Na_0.4Lu_0.6F_2.2: Ce³⁺ crystals, ultraviolet/visible emission, reflection and time-resolved vacuum ultraviolet/ultraviolet excitation spectra were recorded at liquid helium and room temperatures.     

Optical spectroscopy of Yb in the Cs2NaYF6 single crystal

Results of the optical spectroscopy investigation of the cubic paramagnetic center Yb³⁺ ion in the Cs₂NaYF₆ single crystal are presented. The Stark level energies of the Yb³⁺ multiplets are established from absorption, luminescence and excitation luminescence spectra and the crystal field parameters are calculated. Information about the phonon spectra of Cs₂NaYF₆ crystals is obtained from the electron-vibrational structure of the optical absorption and luminescence spectra.