中性和带电小钨团簇的第一性原理研究

采用基于密度泛函理论的第一性原理方法,计算了中性和带电小钨团簇W_n（n＝3—6）的构型,得到了一些能量较低的结构,它们都有可能是团簇的基态.研究发现,这些团簇大多具有较低的自旋多重度：中性小钨团簇为自旋单态或三重态;带电小钨团簇为自旋双重态或四重态.当n>3时,小钨团簇具有三维立体结构.通过拟合光电子谱、计算垂直离化能并与实验值比较,进一步讨论了带负电小钨团簇的基态结构. 关键词： 小钨团簇 构型 密度泛函理论     

Appearance of metallic features in small tungsten clusters

The structures and properties of W_n (n=2--14) clusters were studied by using the density functional theory (DFT) at LSDA level. The most stable structures of W_n (n=2--14) clusters with global minimum were determined. The average binding energy (E_b), the first and second difference of total energy (\itδ E, \itδ₂E), the vertical detachment energy (VDE), and the HOMO-LUMO gap versus the size were also discussed. The abrupt decrease of VDE and HOMO-LUMO gap at size n=8 and 10 implied that tungsten clusters of W₈ and W₁₀ appeared to have metallic features. These changes were also accompanied by the delocalization of electron charge density and the strong hybridization between 5d and 6s orbits in W₈ and W_10 clusters. Our results are in good agreement with the available experimental data.     

Pd-Y微团簇的结构与性质研究

在相对论有效原子实势近似下，用密度泛函理论方法，对Pd_n(n=2,3,4)，Y_n（n=2,3,4）,Pd_nY(n=1,2,3,4)，PdY_n(n=2,3,4)，Pd₂ Y_n(n=2,3,4)团簇的各种可能的几何构型进行全优化计算,得到它们的基态结构和 光谱性质.结果表明，由于 Jahn-Teller效应， Pd₄和Y₄的基态结 构为C_s构型，P d₃和Y₃为C_2v 构型；混合微团簇Pd₃Y，Pd ₄Y，PdY₃，PdY₄ 和 Pd₂Y₄基态为C_s构型.最后计算了团簇的能级分布和最 高占据轨道与最低空轨道之间的能级间隙,分析了团簇的化学活性. 关键词： Pd-Y团簇 有效原子实势 密度泛函     

小分子吸附调控Ti掺杂石墨烯电子结构和磁性的密度泛函理论研究

本文采用基于密度泛函理论的第一性原理方法,研究了气体分子CO、NO、NO_2和SO_2吸附对Ti掺杂石墨烯(Ti G)电子结构和磁性的调制.研究表明:Ti G对CO、NO、NO_2和SO_2分子的吸附作用较强,各分子与Ti原子键合并形成Ti-X键(X代表C、O、N原子);各分子的吸附可导致Gas@Ti G体系电磁性质明显改变:CO分子吸附基底后,虽未能引起CO@Ti G体系电子性质改变和磁性的产生,却能够有效调控该体系的带隙宽度;不同于CO分子,NO、NO_2和SO_2分子的吸附使得半导体性的Ti G基底转变为金属特性,但各体系磁性表征不同:NO@Ti G发生完全自旋极化,即NO分子与基底上均有自旋分布,且二者的自旋方向相同;顺磁性的NO_2分子吸附于Ti G基底时磁性消失;SO_2分子吸附于Ti G基底后自身产生磁性,但基底几乎未发生自旋极化,SO_2@Ti G呈现自旋极化的局域分布特征.由此,依据分子吸附后体系电磁性质特征的不同,可辨识被测气体分子.此项研究结果为高灵敏度和高选择性的石墨烯基气体传感器的设计提供理论参考.     

Geometries, stabilities and electronic properties of small Nb-doped gallium clusters: A density functional theory study

The host Ga_n+1 and doped Ga_nNb (n=1-9) clusters with several spin configurations have been systematically investigated by a relativistic density functional theory (DFT) with the generalized gradient approximation. The optimized equilibrium geometries tend to prefer the close-packed configurations for small Nb-doped gallium clusters up to n=9. The average binding energies per atom (E_b/atom), second-order differences of total energies (Δ₂E), fragmentation energies (E_f) and HOMO-LUMO gaps of Ga_n+1 and Ga_nNb (n=1-9) clusters are studied. The results indicate the doping of Nb atom in gallium clusters improves the chemical activities. In particular, the clusters with sizes of Ga₄Nb and Ga₇Nb are found to be more stable with respect to their respective neighbors. Our calculated vertical ionization potentials (VIPs) exhibit an obvious oscillating behavior with the cluster size increasing, except for Ga₃ and Ga₄Nb, suggesting the Ga₃, Ga₅, Ga₇, GaNb, Ga₃Nb, Ga₆Nb and Ga₈Nb clusters corresponding to the high VIPs. In the case of vertical electron affinities (VEAs) and chemical hardness η, VEAs are slightly increasing whereas chemical hardness η decreasing as Ga_nNb cluster size increases. Besides, the doping of Nb atom also brings the decrease as the cluster sizes increases for atomic spin magnetic moments (μ_b).     

密度泛函理论研究Hg与Auqn(n=1—6, q=0,+1,-1) 团簇的相互作用

采用密度泛函理论中的广义梯度近似对Hg与小团簇Au ^q_n (n=1—6, q=0, +1, -1)的相互作用进行了系统研究. 结果表明,除Au₅^+,-团簇外,前线分子轨道理论可以成功预测大部分Au _n Hg ^q 复合物的最低能量结构. Au_n团簇对Hg的吸附受团簇尺寸大小和团簇所携带电荷的影 关键词： 密度泛函理论 汞 金团簇 吸附能     

Geometric,stable and electronic properties of Aun-2Y2（n=3-8） clusters

Employing first-principles methods,based on the density function theory,and using the LANL2DZ basis sets,the ground-state geometric,the stable and the electronic properties of Aun-2Y2 clusters are investigated in this paper.Meanwhile,the differences in property among pure gold clusters,pure yttrium clusters,gold clusters doped with one yttrium atom,and gold clusters doped with two yttrium atoms are studied.We find that when gold clusters are doped by two yttrium atoms,the odd-even oscillatory behaviours of Aun-1Y and Aun disappear.The properties of Aun-2Y2 clusters are close to those of pure yttrium clusters.     

TiO2分子在GaN(0001)表面吸附的理论研究

采用基于密度泛函理论的平面波超软赝势法,计算了TiO₂分子在GaN(0001)表面的吸附成键过程、吸附能量和吸附位置. 计算结果表明不同初始位置的TiO₂分子吸附后,Ti在fcc或hcp位置,两个O原子分别与表面两个Ga原子成键,Ga-O化学键表现出共价键特征,化学结合能达到7.932-7.943eV,O-O连线与GaN[1120]方向平行,与实验观测(100)[001] TiO₂//(0001)[1120]GaN一致. 通过动力学过程计算分析,TiO₂分子吸附过程经历了物理吸附、化学吸附与稳定态形成的过程,稳定吸附结构和优化结果一致. 关键词： GaN(0001)表面 2分子')" href="#">TiO₂分子 密度泛函理论 吸附     

钇覆盖Si@Al12团簇的贮氢性能

利用密度泛函理论系统地研究了Y_mSi@Al₁₂ (m=1—3)团簇及其贮氢性质. 结果表明, 在所研究的尺度范围内, 钇原子未在Si@Al₁₂团簇上团聚; 每个钇原子按18电子规则吸附氢分子, 其中Y₃Si@Al₁₂团簇可以吸附16个完整氢分子, 贮氢质量分数为5.0 %, 平均吸附能处于0.324—0.527 eV之间, 较为理想的吸附能说明在室温条件下吸氢和脱氢是可行的.     

水分子在Yn (n=2-8)团簇表面的分子吸附与解离吸附

运用密度泛函理论,对H2O在Yn (n=2-8) 团簇表面的分子吸附与解离吸附两种模式进行了结构优化,电子性质分析。结果表明：分子吸附中H2O倾向于O端吸附于Y-Y原子桥位,而解离吸附中H2O解离的H, O原子倾向于吸附于Yn团簇的面位。两种吸附模式都导致了（解离吸附n=4, 5除外）主团簇Y原子平均键长增大。分子吸附和解离吸附的吸附强度和化学活性都随尺寸增加而增大。解离吸附中体系的稳定性明显高于分子吸附,且与体系的电子壳层效应密切相关。     

水分子在Yn (n=2-8)团簇表面的分子吸附与解离吸附

运用密度泛函理论,对H2O在Yn (n=2-8) 团簇表面的分子吸附与解离吸附两种模式进行了结构优化,电子性质分析。结果表明：分子吸附中H2O倾向于O端吸附于Y-Y原子桥位,而解离吸附中H2O解离的H, O原子倾向于吸附于Yn团簇的面位。两种吸附模式都导致了（解离吸附n=4, 5除外）主团簇Y原子平均键长增大。分子吸附和解离吸附的吸附强度和化学活性都随尺寸增加而增大。解离吸附中体系的稳定性明显高于分子吸附,且与体系的电子壳层效应密切相关。     

团簇LaO的理论研究

采用密度泛函理论研究LaO团簇体系。中性分子LaO的基态是两重态(2Σ),阴离子LaO-和阳离子LaO 的基态都是单重态(1Σ)。使用不同的方法计算团簇LaO的电子亲和能和电离能。计算结果表明用BLYP方法和弥散极化基组计算结果和实验数据吻合较好。用含时密度泛函理论计算团簇LaO的低能激发态,从理论上归属LaO-的光电子能谱的谱峰和LaO的吸收光谱的谱峰。计算得到与实验一致的结果。     

含Nb或Ge的锆合金表面氧吸附行为的第一性原理研究

采用基于密度泛函理论的第一性原理方法, 研究了纯锆表面和含Nb或Ge锆合金表面上氧的吸附性质. 结果表明, Nb和Ge对Zr(0001), (1120)和(1010)表面吸附性质的影响各不相同. 根据计算得到的偏聚能结果, Nb和Ge迁移到Zr(0001)表面比迁移到其他两个表面更容易, 而Nb和Ge 都可以降低Zr(0001)表面对氧原子的吸附能力, 因此这两种元素都能抑制锆合金的初始氧化. 进一步的电子结构分析发现, Nb和Ge改变表面对氧原子的吸附能力是通过改变表面d能带的分布来实现的.     

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     

奥硝唑在TiO_2(101)晶面上吸附特征的理论研究

奥硝唑残留是一种新兴污染物,对环境和人类健康具有巨大的威胁.采用密度泛函理论,研究了奥硝唑在锐钛矿TiO_2(101)晶面的吸附特性.优化了奥硝唑在锐钛矿TiO_2(101)晶面的吸附结构,计算了最佳吸附位点,吸附能,态密度,电子结构图.结果表明,当咪唑环上N(3)原子吸附在TiO_2的Ti(5)原子上时,吸附能最大,为最稳定的吸附构型.通过对吸附构型的分析,我们发现C(2)-N(3)键呈现变弱趋势,我们推测奥硝唑在TiO_2表面降解的可能性以及反应活性位点就是咪唑环上C-N键.     

A density functional theory study on the adsorption of CO and O2 on Cu-terminated Cu2O （111） surface

The adsorptions of CO and 02 molecules individually on the stoichiometric Cu-terminatcd Cu20 （111） surface are investigated by first-principles calculations on the basis of the density functional theory. The calculated results indicate that the CO molecule preferably coordinates to the Cu2 site through its C atom with an adsorption energy of-1.69 eV, whereas the 02 molecule is most stably adsorbed in a tilt type with one O atom coordinating to the Cu2 site and the other O atom coordinating to the Cul site, and has an adsorption energy of -1.97 eV. From the analysis of density of states, it is observed that Cu 3d transfers electrons to 2π orbital of the CO molecule and the highest occupied 5σ orbital of the CO molecule transfers electrons to the substrate. The sharp band of Cu 4s is delocalized when compared to that before the CO molecule adsorption, and overlaps substantially with bands of the adsorbed CO molecule. There is a broadening of the 2π orbital of the 02 molecule because of its overlapping with the Cu 3d orbital, indicating that strong 3d-2π interactions are involved in the chemisorption of the 02 molecule on the surface.     

Density functional theory study of MgnNi2 (n=1-6) clusters

The geometries of Mg_nNi₂ (n=1-6) clusters are studied by using the hybrid density functional theory (B3LYP) with LANL2DZ basis sets. For the ground-state structures of Mg_nNi₂ 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 Mg_nNi₂ clusters. The Mg₃ Ni₂ and Mg₅Ni₂ clusters are more stable than neighbouring clusters, and the Mg₄Ni₂ cluster exhibits a higher chemical activity.     

WnNim(n+m=8)团簇结构与电子性质的理论研究

采用密度泛函理论(DFT)中的B3LYP方法,在Lanl2dz基组水平上对W_nNi_m(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;并对基态构型的平均结合能、Wiberg键级(WBI)、磁学性质、NBO进行了分析,结果表明:团簇随着W原子数的增多,稳定性增强,n≥5时,结构中都含有纯钨团簇的结构基元;W-W键级高于W-Ni键和Ni-Ni键;W₅Ni₃,W₆Ni₂团簇发生了"磁矩猝灭"的现象;在W,Ni原子内部,轨道电荷发生了转移,产生了"轨道杂化"现象,W,Ni原子之间也发生了电荷转移形成了较强的化学键. 关键词： nNi_m(n+m=8)团簇')" href="#">W_nNi_m(n+m=8)团簇 几何结构 电子性质 密度泛函理论     

接枝聚合物对小分子的选择性吸附研究

文章应用密度泛函理论研究接枝于壁面的方阱链对二元小分子混合物的选择性吸附特性. 系统的Helmholtz剩余自由能泛函被表示为硬球排斥和方阱吸引两部分贡献之和,分别由硬球链流体状态方程和变阱宽方阱链流体状态方程的简单加权密度近似来进行计算. 用此理论方法,分别考察了接枝聚合物的结构性质,以及不同温度下接枝分子层对二元方阱流体的选择性吸附性能. 结果表明:分子刷厚度随接枝密度线性增长而随温度非线性增加,并且在高温下趋于饱和;在较低温度下,接枝聚合物刷能表现出很好的选择性吸附能力,当聚合物刷被加热到高于饱和温度时,该能力将大幅度地减弱. 关键词： 密度泛函理论 接枝聚合物 选择性吸附 方阱链     

Density functional theory study of Mg_2Ni_n(n= 1–8) clusters

The density functional theory B3PW91 with LANL2DZ basis sets has been used to study the possible geometries of Mg2Nin(n = 1–8) clusters. For the lowest energy structures of the clusters, stabilities, electronic properties, and natural bond orbital(NBO) are calculated and discussed. The results show that the doped Mg atoms reduce the stabilities of pure Ni clusters. The Mg2Ni2, Mg2Ni4, and Mg2Ni6clusters are more stable than neighboring clusters. The system appears magic number characteristics. In addition, the hybridization phenomenon occurs, owing to the interaction of Mg and Ni. The result of charge transfer is that Ni atom is negative and the Mg atom is positive. We also conclude that the 3p and 4d orbitals of the Ni atom have an effect on the stabilities of the clusters.