First-Principles Study of Geometries,Stabilities and Electronic Properties of Ca2Sin （n=1-11） Clusters

The equilibrium geometries, relative stabilities, and electronic properties of Ca2Sin （n = 1-11） clusters have been systematically investigated by using the density function theory at the 6-311G （d） level The optimized geometries indicate that the most stable isomers have three-dimensional structures for n = 3-11. The electronic properties of Ca2 Sin （n = 1-11） dusters axe obtained through the analysis of the natural charge population, natural electron configuration, vertical ionization potential, and vertical electron affinity. The results show that the charges in corresponding Ca2Sin clusters transfer from the Ca atoms to the Sin host. Based on the obtained lowest-energy geometries, the size dependence of cluster properties, such as averaged binding energies, fragmentation energies, second-order energy differences, HOMO- LUMO gaps and chemical hardness, are deeply discussed.     

AunLa(n=1-8)团簇的密度泛函研究

采用密度泛函理论（DFT）中的杂化密度泛函B3LYP方法,在LANL2DZ基组水平上研究了AunLa (n=1-8)团簇的几何结构。计算并讨论了基态结构稳定性及电子性质。结果表明,当n=3-8时,基态结构均为三维结构且La原子趋向与更多的Au原子结合。团簇二阶能量差分,能隙和化学硬度计算结果显示除了AuLa外,具有偶数数目的团簇比奇数数目的团簇具有更好的稳定性,其中,Au3La团簇的稳定性相对较好。     

BnTi(n=1-12)团簇的结构, 电子性质和磁性

利用密度泛函理论广义梯度近似方法得到了BnTi(n=1-12)团簇的基态结构, 并讨论了电子性质和磁性质. 结果表明, n≤5 时, BnTi 基态结构呈平面或准平面, n>5 时, Ti 原子倾向于与较多的B 原子成键而呈三维结构. 由二阶能量差分得出B3Ti, B5Ti, B10Ti 为幻数团簇. Mulliken 布居分析显示BnTi 团簇中电荷由Ti 原子向近邻B 原子转移且以共价键与离子键共存; 除BTi 磁矩为5 μB 外, 其余团簇磁矩处于0-2 μB 之间; 团簇总磁矩主要由Ti 原子的3d 轨道和个别B 原子提供. B3Ti和B7Ti 团簇中, B 原子表现为反铁磁性.     

BnTi(n=1-12)团簇的结构, 电子性质和磁性

利用密度泛函理论广义梯度近似方法得到了BnTi(n=1-12)团簇的基态结构, 并讨论了电子性质和磁性质. 结果表明, n≤5 时, BnTi 基态结构呈平面或准平面, n>5 时, Ti 原子倾向于与较多的B 原子成键而呈三维结构. 由二阶能量差分得出B3Ti, B5Ti, B10Ti 为幻数团簇. Mulliken 布居分析显示BnTi 团簇中电荷由Ti 原子向近邻B 原子转移且以共价键与离子键共存; 除BTi 磁矩为5 μB 外, 其余团簇磁矩处于0-2 μB 之间; 团簇总磁矩主要由Ti 原子的3d 轨道和个别B 原子提供. B3Ti和B7Ti 团簇中, B 原子表现为反铁磁性.     

Structures and Electronic Properties of CuN （N≤13） Clusters

A systematic study on the structures and electronic properties of copper clusters has been performed using the density functional theory. In the calculation, there are many isomers near the ground state for small copper clusters. Our results show that the three-dimensional isomers of copper clusters start from Cu7 cluster and then show a tendency to form more compact structures. The results of the formation energy and the second derivative of binding energy with duster size show that besides N = 8, N =11 is also a magic number. Furthermore, it is the first time to find that the ground state of 11-atom clusters is a biplanar structure as same as the 13-atom cluster. The clear odd-even alternation as cluster size for the formation energy indicates the stability of electronic close shell existed in the range studied.     

Nin(n=1-9)小团簇的密度泛函理论研究

采用密度泛函理论(DFT)方法对Nin(n=1-9)团簇的结构, 稳定性和磁性进行了详细的研究. 得到了一些以前文献中没有提到的稳定结构, 并与其它方法得到的结构进行了比较, 得到的最稳定结构与实验结果相一致. 团簇能量的二阶差分、分裂能、HOMO-LUMO能隙随团簇尺寸的演化都没有表现出明显的奇偶振荡行为, 但在n=5、7时均有较大的值, 说明相对应的团簇具有较高的稳定性、较低的化学活性. 团簇磁性的研究表明团簇的平均每原子磁矩随团簇尺寸的增加有一定振荡, 但有逐渐减小的趋势, n≥5时团簇的构型对团簇磁性的影响较小.     

基于密度泛函理论的PdnZr（n=2-8）团簇的结构和性质研究

利用密度泛函理论中的B3LYP/LanL2DZ方法对PdnZr (n = 2–8)团簇的几何结构、稳定性、电子性质进行了研究。在优化出的结构的基础上,讨论了PdnZr (n = 2–8) 团簇的生长模式,计算了团簇基态的平均结合能,离解能,二阶能量差分以及最高占据轨道与最低空轨道之间的能隙。研究表明,较大尺度的PdnZr (n = 2–8)团簇的基态是通过在Pdn-1Zr的基础上增加一个Pd原子并与其中的Zr原子相连而形成的;在纯钯团簇中掺杂锆原子后可以提高团簇的稳定性,多数情况下可以降低团簇的化学反应活性;PdnZr(n=2-8)基态团簇中的电荷转移总是从Zr原子到其他Pd原子。     

RuSin（n=1～6）团簇的结构、稳定性和电子性质的密度泛函研究

运用杂化密度泛函理论方法在(U)B3LYP/LanL2DZ水平研究了RuSin(n=1~6)团簇体系的稳定结构及电子性质．结果发现：RuSin(n=1~6)团簇基本保持了纯硅团簇的框架.对原子平均束缚能和分裂能的计算表明,RuSi6团簇是RuSin(n=1~6)团簇中热力学稳定性最强的.对自然电荷分布的研究结果发现,RuSin(n=2,4～6)团簇的最低能结构出现电荷反转现象. HOMO-LUMO能隙的研究结果表明掺入钌原子后团簇的化学活性增强了,且RuSi的化学活性是RuSin(n=1~6)团簇最强的。通过对团簇磁矩的研究发现,RuSi和RuSi3团簇具有了磁性,其余团簇的总磁矩为零,且RuSin(n=1～6)团簇中各原子对团簇总磁矩的贡献不同.     

Density Functional Study of Physical and Chemical Properties of Nano Size Boron Clusters: Bn (n=13～20)

采用密度泛函理论B3LYP与6-311++G方法研究了硼簇B_n(n=13～20)的电子和几何结构、总能量、结合能、谐波频率、点对称性、电荷分布、偶极矩、化学键以及最高分子占据轨道和最低分子占轨道能量差．此外,借助第一和第二能级差确定最稳定的硼簇尺寸．研究表明硼簇几乎所有的物理性质有尺寸依赖性,双环管状结构的B₂₀具有最高平均结合能．内有一原子的二十面体结构的B₁₃不具有稳定构型,这种结构转变为开放式笼状．B₂₀出现二维到三维的结构转变．Mulliken分析表明电荷分布有x-z和y-z平面对称．硼簇的平面稳定性可以通过离域键(π键和α键)以及多中心键来解释．     

Agn-1Si（n=5-10）团簇结构与性质研究

采用密度泛函理论研究了Agn-1Si团簇（n = 5-10）的几何结构和物理性质。首先得到体系最低能量结构,其中Ag5Si 和 Ag7Si团簇的结构比之前研究中结构能量更低。通过分析相应结构的能隙,平均结合能,二阶能量差可以发现Si原子的加入可以加强团簇结构稳定性,使团簇更加紧凑。在团簇尺寸n = 5-10的范围里,拥有八个价电子的Ag4Si团簇在以上三个方面都显示出非常稳定的特点。通过分析Agn-1Si团簇 (n = 5-10)的差分电荷发现,电荷的转移主要发生在Si原子与其相邻的Ag原子之间, Si原子和附近的Ag原子之间产生了强烈的共价相互作用,是团簇稳定性增强的重要原因。     

Configurations, Electronic Structure and Magnetic Ordering of Small Manganese Clusters

We investigate the configurations, electronic structures, and magnetic ordering of MnN （N = 2-13） clusters based on all-electron density functional theory. The Jahn-Teller effect plays an important role in determining the ground state of certain geometries. The magnetic ordering of the MnN dusters transits from ferromagnetic ordering for the smallest （ N = 2, 3） dusters to a near degeneracy state including ferromagnetic and ferrimagnetic ordering in the vicinity of N = 4-6 and to a clear ferrimagnetic ordering at N = 7 or beyond. N = 6 and 10 are the magic numbers for neutrai MnN （N = 2-13） dusters.     

First-Principles Calculations for Structures and Melting Temperature of Si6 Clusters

We investigate the structures and the melting temperature of the Si6 cluster by using the first-principles pseudopotential method in real space and Langevin molecular dynamics. It is shown that the ground structure of the Si6 cluster is a square bipyramid, and the corresponding melting temperature is about 1923 K. In the heating procedure, the structures of the Si6 cluster change from high symmetry structures containing 5-8 bonds, via prolate structures containing 3-4 bonds, to oblate structures containing 1-2 bonds.     

Stability and Growth Modes of Ni--C Clusters: A Study based on All-Electron Density Function Theory

Growth modes of the free-standing NiCN （N ≤ 8） and Ni2CN （N ≤ 8） dusters are investigated by the allelectron density functional theory. The results reveal that there are two competing modes for the growth of these clusters： the linear chain and the ring structure without transannular bonds. The lowest-energy geometries of NiCN （N ≤ 8） are the linear chains with the Ni atom at one end, except for NiC2 and NiCT. The Ni2CN （N ≤ 8） clusters all prefer to the linear chains with the two Ni atoms at the two ends. Miilliken population analysis indicates that the total spin of the lowest-energy cluster show significant odd-even alternation. The NiMCN （M = 1,2） clusters with the even N are one and those with the odd-N are zero.     

Ptn(n=1-9)团簇结构及磁性的第一性原理计算

采用密度泛函理论中的广义梯度近似泛函BPW91和三参数杂化密度泛函B3LYP研究Ptn团簇的结构,稳定性和磁性.两种方法得到了相同的稳定结构,基态结构也相同,只是次稳定结构的稳定顺序稍有不同.两种方法得到的平均配位数和平均键长有相似的变化规律,总体上随团簇尺寸的增大而增大,n=2-3时增幅较大,n=4-9时增幅较小,且有一定的振荡.两种方法得到团簇能量的二阶差分、分裂能、HOMO-LUMO能隙随团簇尺寸的演化都没有表现出明显的奇偶振荡行为,但在n=2、5、8时均有较大的值,说明相对应的团簇具有较高的稳定性.两种方法得到团簇的平均每原子磁矩随团簇尺寸的增大有逐渐减小的趋势,个别团簇有振荡.结果表明两种泛函都可以描述团簇结构、稳定性和磁性.     

Electronic structure and magnetism in (CoPt)n(n⩽5) clusters

The geometrical and magnetic properties of bimetallic clusters (CoPt)_n(1?n?5) have been studied by using the generalized gradient correction spin density formalisms. In general, the ground state structures of (CoPt)_n clusters are the three-dimension structures. We found that both the binding energy and magnetism per (CoPt) unit are increasing consistently with the size of the Co–Pt cluster (n). However, as the n increases, the magnetism shows a trace of convergence while the binding energy shows a linearly increasing pattern. Generally, Co average magnetic moment is enhanced when alloyed with Pt atoms than that in pure Co clusters.     

First-Principles Calculations for Thermodynamic Properties of Perovskite-Type Superconductor MgCNi3

The ground state properties and equation of state of the non-oxide perovstdte-type superconductor MgCNi3 are investigated by first-principles calculations based on the plane-wave basis set with the local density approximation （LDA） as well as the generalized gradient approximation （GGA） for exchange and correlation, which agree well with both theoretical calculations and experiments. Some thermodynamic properties including the heat capacity, the thermal expansion coefficient and the Griineisen parameter for perovskite structure MgCNi3 are obtained. The dependences of these thermodynamic properties on pressure and temperature are given for the first time.     

Study of (Al2O3)n(Ox) clusters with n = 16 and x = 0, 1, 2 from first principles calculations

The ionic and electronic structure of (Al₂O₃)_n(O_x) clusters with n 16 and x = 0, 1, 2 is studied by means of first principles density functional calculations, norm-conserving pseudopotentials and a numerical atomic basis set. The equilibrium geometries have been determined by total energy minimization, starting with several initial geometries for each cluster size. The trends obtained for the atomic arrangements (structural isomers, coordination numbers, disordered versus ordered structures, etc.) and the electronic properties (binding energies, Homo-Lumo gap and dipole moments) are discussed. For most of the oxidized clusters studied here we find that the Homo-Lumo gap and the magnitude of dipole moment of isomeric species can vary drastically.