第一性原理计算LiNBe(N=1～12)团簇的基态结构及其电子性质

从第一性原理出发利用密度泛函理论(DFT)计算了LiNBe(N=1-12)团簇的基态结构及其电子性质.计算结果表明:铍掺杂锂团簇LiNBe(N=1-12)的基态结构相当于Be原子取代LiN 1主团簇基态结构中一个Li原子的位置;当团簇尺寸N≥6时,杂质原子Be被束缚在主团簇笼子内;随着团簇尺寸增大,团簇的离解能和二阶能量差分均出现了奇-偶振荡;从结构稳定性上来看,Li6Be是个幻数团簇.     

第一性原理研究掺杂及未掺杂(TiO_2)_3团簇的电子性质（英文）

为了研究金属掺杂团簇时带隙的变化趋势,本文用Cr,Mo,V,Nb四种元素掺杂(TiO_2)_3团簇,并用密度泛函理论下的广义梯度近似(GGA)方法计算.不同掺杂位置的结果表明最好的掺杂位置是3-配位的钛位置.所有掺杂后(TiO_2)_3团簇的HOMO-LUMO带隙都要比未掺杂时要小,对应高能区态密度峰值左移0.1 e V;HOMO的电子云分布主要占据了氧原子的位置,当掺杂团簇被激发时,电子从末端氧原子位置跃迁到掺杂原子.此外,我们进一步的计算表明Cr和Mo是降低(TiO_2)_3团簇带隙较好的掺杂元素.为了进一步的研究掺杂(TiO_2)_3团簇的性质以及它在光催化,清洁能源等方面的应用,还需要我们进行实验和理论相结合的研究.     

双层石墨烯吸附碱金属原子的第一性原理研究

基于密度泛函的第一性原理方法,研究了Li、Na、K和Rb碱金属原子吸附在双层石墨烯(BLG)表面的吸附能、迁移行为、电子性能.研究发现,Li和Na原子在BLG表面吸附易形成团簇,K和Rb原子能够分散吸附.碱金属原子在BLG表面的扩散能垒随原子半径的增加而减小.碱金属原子吸附使电子部分转移至BLG,使体系Fermi能级贯穿导带,表现出金属性.电荷密度差和电荷转移的分析表明,Li、Na、K和Rb与BLG表面以离子键结合.     

团簇Aun+1-1、AunCr-1 (n=1-10)吸附CO的密度泛函理论研究

采用密度泛函理论对CO在阴离子团簇Aun+1-1、AunCr-1(n=1-10))表面的吸附做了系统研究.结果表明,团簇Aun+1CO-1、AunCrCO-1的基态结构是在团簇Aun+1-1、AunCr-1最低能量结构的基础上吸附CO形成; 吸附后的CO键长变长,振动频率减小,表明CO分子被活化;取值相同时,AunCrCO-1的平均结合能高,表明团簇Aun+1CO-1掺杂Cr后稳定性升高.HOMO-LOMO能隙结果表明Aun+1CO-1替代掺杂Cr原子后团簇的化学活性得到了提升,AunCrCO-1、Aun+1CO-1团簇能隙具有奇偶振荡的现象;轨道电荷分析表明CO与团簇相互作用实质是C原子与成键Au原子或Cr原子间转移电荷,CO在与团簇相互作用过程中O原子轨道电荷分布几乎没有发生变化.     

Ge( SiO2)n团簇结构和电子性质的密度泛函理论研究

采用密度泛函理论中的广义梯度近似(GGA)对Ge(SiO2)n(n=1～7)团簇的几何构型进行优化,并对能量、频率和电子性质进行了计算.结果表明,Ge(SiO2)n的最低能量结构是在(SiO2)n端位O原子以及近邻端位O原子的Si原子上吸附一个Ge原子优化得到;随着锗原子数的增加,增加的锗原子易与原来的锗原子形成锗团簇.掺杂锗原子后团簇的能隙比(SiO2)n团簇的能隙小,当多个Ge原子掺杂到(SiO2)3团簇时,其能隙随着Ge原子个数的增加出现了振荡,Gem(SiO2)3的能隙从可见光区到近红外光区变化.二阶能量差分、分裂能表明Ge(SiO2)2和Ge(SiO2)5团簇是稳定的.     

NO与Au_nMg~(-1)、Au_n~(-1)(n=1-8)的相互作用的密度泛函理论研究

本文采用密度泛函理论对NO在阴离子团簇Au_nMg~(-1)、 Au_n~(-1)(n=1-8)表面的吸附做了系统研究.结果表明,团簇Au_nMgNO~(-1)、 Au_nNO~(-1)的基态与亚稳定结构是在团簇Au_nMg~(-1)、 Au_n~(-1)最低能量结构的基础上吸附NO形成, NO的吸附没有改变团簇Au_nMg~(-1)、 Au_n~(-1)的最低能量结构;吸附后的NO键长变长,表明NO分子被活化,此外吸附后的NO均带负电;计算表明团簇Au_nMgNO~(-1)、 Au_nNO~(-1)吸附能都具有奇偶振荡的现象,取值相同时, Au_nMgNO~(-1)的吸附能较低,表明团簇Au_nNO~(-1)掺杂Mg后稳定性降低; HOMO-LOMO能隙结果表明AuMgNO~(-1)活性最低,总体上Au_nNO~(-1)掺杂Mg原子后团簇的化学活性降低.     

双层石墨烯吸附碱金属原子的第一性原理研究

基于密度泛函的第一性原理方法，研究了Li、Na、K和Rb碱金属原子吸附在双层石墨烯(BLG)表面的吸附能、迁移行为、电子性能. 研究发现，Li和Na原子在BLG表面吸附易形成团簇，K和Rb原子能够分散吸附. 碱金属原子在BLG表面的扩散能垒随原子半径的增加而减小. 碱金属原子吸附使电子部分转移至BLG，使体系Fermi能级贯穿导带，表现出金属性. 电荷密度差和电荷转移的分析表明，Li、Na、K和Rb与BLG表面以离子键结合.     

密度泛函理论研究NO与AunMg-1、Aun-1 (n=1-8)的相互作用

本文采用密度泛函理论对NO在阴离子团簇AunMg-1、Aun-1 (n=1-8)表面的吸附做了系统研究.结果表明, 团簇AunMgNO-1、AunNO-1的基态与亚稳定结构是在团簇AunMg-1、Aun-1最低能量结构的基础上吸附NO形成,NO的吸附没有改变团簇AunMg-1、Aun-1的最低能量结构;吸附后的NO键长变长, 表明NO分子被活化,此外吸附后的NO均带负电；计算表明团簇AunMgNO-1、AunNO-1吸附能都具有奇偶振荡的现象,取值相同时，AunMgNO-1的吸附能较低，表明团簇AunNO-1掺杂Mg后稳定性降低；HOMO-LOMO能隙结果表明AuMgNO-1活性最低、总体上AunNO-1掺杂Mg原子后团簇的化学活性降低.     

第一性原理研究掺杂及未掺杂(TiO2)3团簇的电子性质

为了研究金属掺杂团簇时带隙的变化趋势,本文用Cr, Mo, V, Nb四种元素掺杂 (TiO2)3团簇,并用密度泛函理论下的广义梯度近似（GGA）方法计算。不同掺杂位置的结果表明最好的掺杂位置是3-配位的钛位置。所有掺杂后(TiO2)3团簇的HOMO-LUMO带隙都要比未掺杂时要小,对应高能区态密度峰值左移0.1eV;HOMO的电子云分布主要占据了氧原子的位置,当掺杂团簇被激发时,电子从末端氧原子位置跃迁到掺杂原子。此外,我们进一步的计算表明Cr和Mo是降低(TiO2)3团簇带隙较好的掺杂元素。为了进一步的研究掺杂(TiO2)3团簇的性质以及它在光催化,清洁能源等方面的应用,还需要我们进行实验和理论相结合的研究。     

第一性原理研究掺杂及未掺杂(TiO2)3团簇的电子性质

为了研究金属掺杂团簇时带隙的变化趋势，本文用Cr, Mo, V, Nb四种元素掺杂 (TiO2)3团簇，并用密度泛函理论下的广义梯度近似（GGA）方法计算。不同掺杂位置的结果表明最好的掺杂位置是3-配位的钛位置。所有掺杂后(TiO2)3团簇的HOMO-LUMO带隙都要比未掺杂时要小，对应高能区态密度峰值左移0.1eV；HOMO的电子云分布主要占据了氧原子的位置，当掺杂团簇被激发时，电子从末端氧原子位置跃迁到掺杂原子。此外，我们进一步的计算表明Cr和Mo是降低(TiO2)3团簇带隙较好的掺杂元素。为了进一步的研究掺杂(TiO2)3团簇的性质以及它在光催化，清洁能源等方面的应用，还需要我们进行实验和理论相结合的研究。     

Strong dependence of ferrimagnetic properties on Na concentration in Na-K alloy clusters incorporated in low-silica X zeolite

Na concentration (x) dependence of ferrimagnetic properties is investigated for Na-K alloy clusters incorporated in low-silica X (LSX) zeolite. In the LSX zeolite, β-cages of inner diameter ≈7 Å are arranged in a diamond structure, and supercages of inner diameter ≈13 Å are formed among them. The used LSX zeolite contains xNa⁺ and (12−x)K⁺ cations per β-cage or supercage. Guest nK atoms are loaded into the zeolite, namely the loading density is given by n per β-cage. The samples at x=4 have been reported to show Néel’s N-type ferrimagnetism in the specific region of n. This ferrimagnetism is explained by the model of antiferromagnetic coupling between two non-equivalent magnetic sublattices of clusters, the ones in β-cages and the others in supercages. In the present study, the value of x is changed from 4 to 0. Ferrimagnetic properties are found to show strong x-dependence. A systematic increase in loading densities of ferrimagnetic region is clearly observed with decreasing x. A remarkable change in temperature dependence of spontaneous magnetization is observed depending on x. Na⁺ cations are known to be mainly distributed in β-cages. Hence, the decrease in Na concentration is proposed to change the electronic potential depth for clusters in β-cage, which leads to important differences in the interaction between electrons localized in β-cages and those in supercages.     

First principles study the ferromagnetic properties and electronic structure of boron doped ZnSe

Using the full-potential linearized augmented plane wave method with generalized gradient approximation, the magnetic properties and the electronic structure of the boron-doped ZnSe (zinc blende phase) are investigated. Spin polarization calculations show the magnetic moment of the 64-atoms supercell containing one B_Se (B_Zn) is 3.00 (0.015) μ_B. The density of states indicates the magnetic moments of the B_Se doped configuration mainly come from the doped boron atoms and a few from its neighboring zinc atoms. The ferromagnetic and antiferromagnetic calculations for several doped configurations suggest B_Se could induce stable ferromagnetic ground state in ZnSe hosts and ferromagnetic couplings exist between the doped boron atoms. Electronic structures show that B_Se is p-type ferromagnetic semiconductor and hole-mediated double exchange is responsible for the ferromagnetism, while the B_Zn doped configuration is n-type semiconductor. Relative shallow acceptor and donor levels indicate boron-doped ZnSe is ionized easily at working temperatures.     

锂原子修饰B6团簇的储氢性能研究

利用密度泛函理论研究B₆和Li_mB₆ (m= 1–2)团簇的结构及其储氢性能. 结果表明, 氢分子在B₆团簇的三种可能结构中均发生解离吸附, Li原子在B₆团簇表面不发生团聚,每一个Li原子均吸附几个氢分子. 其中以两个Li原子修饰笼形B₆团簇吸附完整氢分子数最多,储氢质量分数为20.38%, 氢分子的平均吸附能为1.683 kcal/mol,表明了它在常温常压条件下作为储氢材料的可行性. 关键词： mB₆ (m=1-2)团簇')" href="#">Li_mB₆ (m=1-2)团簇 密度泛函理论(DFT) 吸附能 储氢性能     

Magnetic properties of heusler alloys Ni3−xMnxSn

Heusler alloys with composition corresponding to x = 1, 1.2, 1.3, 1.5, 1.65, 1.8 and 1.9 have been prepared. The saturation magnetization and the paramagnetic moment show a maximum at x = 1.3. The manganese atoms are distributed over octahedral and tetrahedral sites with different magnetic moments (μ_ferro(oct.) = 4μ_B, μ_ferro(tetr.) = 0μ_B). Furthermore there is a certain degree of Mn/Sn disorder with Mn atoms on Sn-sites coupled antiferromagnetically to the Mn sublattice. Using a x_g versus 1/H plot, considerable temperature independent paramagnetism is found far below the Curie-temperature (80 K).     

Spin and orbital magnetic moments and spin anisotropy energies of light rare earth atoms embedded in graphene: A first-principles study

The geometries, electronic structures, spin magnetic moments (SMMs), orbital magnetic moments (OMMs) and spin anisotropy energies (SAEs) of light rare earth atoms (La, Ce, Pr, Nd, Pm, Sm, Eu, and Gd) embedded in graphene were studied by using first-principles calculations based on Density Functional Theory (DFT). The spin-orbital coupling effect was taken into account and GGA+U method was adopted to describe the strongly localized and correlated 4f electrons. There is a significant deformation of the graphene plane after doping and optimization. The deformation of Gd doped graphene is the largest, while Eu the smallest. The results show that the valence is +3 for La, Ce, Pr, Nd, Pm, Sm and Gd, and +2 for Eu. Except Eu and Gd, there are obvious OMMs. When the spin is in the Z direction, the OMMs are −0.941 μ_B, −1.663 μ_B, −3.239 μ_B, −3.276 μ_B and −3.337 μ_B for Ce, Pr, Nd, Pm and Sm, respectively, and point the opposite direction of SMMs. All the doped systems except Gd show considerable SAEs. For Ce, Pr, Nd, Pm, Sm, and Eu, the SAEs are −0.928 meV, 20.941 meV, −8.848 meV, 7.855 meV, 75.070 meV and 0.810 meV, respectively. When the spin orientation is different, different orbital angular moments lead to apparent charge density difference of the 4f atoms, which can also explain the origin of SAEs.     

Neutron diffraction study of β-UD3 and β-UH3

The results of a neutron powder diffraction study on β-UD₃ and β-UH₃ are reported. Diffraction patterns have been obtained both above (220 K) and below (10 K) the Curie temperature, in order to refine the crystal structure on the basis of a large number of resolved Bragg peaks and to obtain the ordered magnetic moment. The two kinds of uranium atoms present in the structure appear to be magnetically equivalent. The observed magnetic moment for β-UD₃ at T = 10 K is μ_ord = (1.45 ? 0.11) μ_B/U_atom     

Theory of localized magnetic moments in metals I finite cluster approach

The origin of localized magnetic moments formation in metals is investigated theoretically using a self-consistent local spin density molecular cluster approach. Clusters with up to 55 atoms are employed to describe isolated impurity local moment behavior in the cases of Fe$\text{Ag}$ and Fe$\text{Pd}$. Densities of states and spin magnetic moments were determined and compared with results of spectroscopic (notably photoemission) and magnetization measurements, respectively. In the case of a noble metal host, the spin magnetization density is found to be highly localized around the Fe site; the iron moment is ≈ 3.9μ_B and the polarization of the host Ag atoms is small. In the case of a transition metal host, the iron moment is ≈ 3.2 μ_B but here the strong hybridization of the Fe-3d and Pd-4d states results in a large induced magnetic moment in the host PD metal — in essential agreement with experiment for this giant moment system.     

Magnetic structure and crystal field in cerium compounds with CsCl-type structure

Neutron diffraction and spectroscopy experiments have been performed on the cubic (CsCl-type structure) compounds CeAg, CeZn and CeMg. CeAg orders ferromagnetically with a moment μ_F= 0.8μ_B at 1.7 K. CeZn and CeMg are antiferromagnets; at 4.2 K their magnetic moments are 1.95 μ_B (CeZn) and 1.85 μ_B (CeMg). In the ordered state, they reveal a strong quadratic distortion, the (c/a ? 1) value reaching 1.9% in CeAg at 1.7 K; in CeAg additional atoms shifts seem to be present in the tetragonal cell. Crystal field parameters have been determined as |A₄ 〈r₄〉| = 117 K (CeAg), 74 K (CeZn) and 117 K (CeMg); the consistence of the results with all the previous studies is discussed.     

x射线磁性圆二色吸收谱分析Co膜厚度对原子磁矩和自旋磁矩的影响

利用软x射线磁性圆二色吸收谱(XMCD)研究了Si衬底上沉积的不同厚度的Co膜的轨道磁矩和 自旋磁矩.样品是磁控溅射方法制备的，膜的厚度分别是2nm,10nm和30nm，并在表面覆盖0.8 —1nm厚的金膜防止样品的氧化.根据XMCD求和定则计算得到的轨道磁矩和自旋磁矩分别是0. 249—0.195μ_B(玻尔磁子)和1.230—1.734μ_B.随着膜厚的减小，C o原子的轨道磁矩增加，而自旋磁矩下降.轨道磁矩与总磁矩的比值由0.101上升至0.168，即 2nm膜中Co原子的轨道磁矩对总磁矩的贡献比30nm膜中Co原子的大了83%. 关键词： x射线磁性圆二色 磁性薄膜 轨道磁矩和自旋磁矩 厚度效应