NO在Yn(n=1–12)团簇表面的解离性吸附

采用基于密度泛函理论中的广义梯度近似,在考虑自旋多重度的情况下,对Y_nNO（n=1–12）团簇进行了构型优化,以及稳定性和成键特性分析,结果表明：n=5,7,8,10时,NO吸附使相应的Y_n团簇基态结构发生了明显变化,吸附后,所有尺寸中的N–O键长明显伸长,振动频率减弱,表明NO在Y_n团簇表面发生的是解离性吸附,N–Y,O–Y键的共同作用使Y_nNO团簇具有很大的吸附能;特别是n=3,5,8时,N–O键断裂,吸附能值分别为9.92,9.24,9.82 eV. Y_nNO和Y_n 的二阶能量差分变化趋势表明,NO 吸附对Y_n团簇稳定性和成键特性均产生较大影响. N,O原子sp³轨道杂化时孤对电子的出现导致N–O键断裂,增强了N–Y和O–Y间的成键能力,使Y₃NO,Y₅NO,Y₈NO团簇表现出了很好的稳定性. 关键词： 团簇 NO吸附 基态结构 稳定性     

Wn (n= 1–6)团簇吸附CO的密度泛函研究

采用密度泛函理论(density functional theory, DFT) 在B3LYP/LANL2DZ基组水平上对钨团簇吸附CO分子进行了系统研究. 结果表明, W_nCO团簇的基态结构是在W_n团簇中性或阴离子基态结构的基础上吸附CO生长而成; CO的吸附以端位吸附为主,桥位吸附为辅; CO分子在W_n团簇表面发生的是非解离性吸附. 与优化的CO键长(0.116 nm)相比,吸附后C-O键长变长(0.120–0.123 nm), 表明吸附后C-O键被削弱, CO分子被活化了.稳定性分析表明,在所研究的团簇中, W₃CO和W₅CO团簇的稳定性较强;自然键轨道(NBO)分析表明, W原子与CO分子相互作用的本质是CO分子内的杂化轨道与W原子6s, 5d, 6p和6d轨道相互作用的结果. 关键词： nCO (n= 1–6)团簇')" href="#">W_nCO (n= 1–6)团簇 基态构型 稳定性 电子性质     

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.     

A density functional theoretical investigation of RhSin（n = 1-6） clusters

This paper computationally investigates the RhSin （n = 1 6） clusters by using a density functional approach. Geometry optimizations of the RhSin （n = 1 6） clusters are carried out at the B3LYP level employing LanL2DZ basis sets. It presents and discusses the equilibrium geometries of the RhSin （n = 1-6） clusters as well as the corresponding averaged binding energies, fragmentation energies, natural populations, magnetic properties, and the energy gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital. Theoretical results show that the most stable RhSin（n = 1-6） isomers keep an analogous framework of the corresponding Sin＋1 clusters, the RhSi3 is the most stable cluster in RhSin （n = 1-6） isomers. Furthermore, the charges of the lowest-energy RhSin （n = 1-6） clusters transfer mainly from Si atom to Rh atom. Meanwhile, the magnetic moments of the RhSin（n = 1-6） arises from the 4d orbits of Rh atom. Finally, compared with the Sin＋1 cluster, the chemical stability RhSin clusters are universally improved.     

Density functional study of Agn-1Y (n=2-10) clusters

Employing the density functional theory, we investigate the lowest-energy geometric, the stable and the electronic properties of Ag_n-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 Ag_n and Ag_n-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 Ag_n clusters are greatly changed. In addition, the thermodynamic stabilities of the Ag_n clusters are enhanced generally with the doping of the Y atoms. In addition, the chemical stabilities of the Ag_n-1Y clusters are still improved compared with that of the three-dimensional Ag_n clusters.     

A density-functional theory for (BAs)n clusters (n=1 14): structures, stabilities and electronic properties

This paper investigates the lowest-energy structures,stabilities and electronic properties of (BAs) n clusters (n=1-14) by means of the density-functional theory.The results show that the lowest-energy structures undergo a structural change from two-dimensional to three-dimensional when n=4.With the increase of the cluster size (n 6),the (BAs) n clusters tend to adopt cage-like structures,which can be considered as being built from B 2 As 2 and six-membered rings with B-As bond alternative arrangement.The binding energy per atom,second-order energy differences,vertical electron affinity and vertical ionization potential are calculated and discussed.The caculated HOMO-LUMO gaps reveal that the clusters have typical semiconductor characteristics.The analysis of partial density of states suggests that there are strong covalence and molecular characteristics in the clusters.     

Hydrogen storage capabilities of the most stable isomers of NanBm (m+n=6) clusters

The most stable isomers of NanBm(m+n=6) clusters and their hydrogen storage properties are investigated by means of density functional theory with a 6-311+G(d) basis set. To study the hydrogen storage properties,all of the stable structures of Na n BmHx (m+n=6) clusters have been optimized. It shows that boron atoms of Na n B m are separated from the other boron atoms,and form satellite BHx (x=3,4) clusters around the centre,which attach to the system by a bridging bond of a hydrogen atom or an Na atom. Compared with the hydrogen storage capabilities,the Na3B3 has the highest hydrogen storage capacity among Na n B m clusters. The binding energies,interaction energies of hydrogen atom with Na n B m clusters and second difference in energy of Na3B3Hx clusters have been calculated. The results show that the stability of the Na n B m H x clusters present an odd-even oscillatory effect,as the number of H atoms increases.     

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)团簇的极性和光谱性质的理论研究

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.     

PdnPbm(n+m≤5)混合团簇的结构与光谱性质

在相对论有效原子实势(RECP)近似下，用密度泛函中的B3LYP/LANL2DZ方法，对纯Pb_n(n=2—5)团簇、Pd_nPb_m(n+m≤5)混合团簇的各种可能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；从结构和振动光谱两个方面分析了其形成规律；最后计算了团簇的能级分布和最高占据轨道(HOMO)与最低空轨道(LUMO)之间的能级间隙(HLG)，分析了团簇的化学活性. 关键词： 团簇 有效原子实势 密度泛函     

Structures and electronic properties of Mo2nNn（n=1-5）:a density functional study

The lowest-energy structures and the electronic properties of Mo2nNn(n=1-5) clusters have been studied by using the density functional theory(DFT) simulating package DMol 3 in the generalized gradient approximation(GGA).The resulting equilibrium geometries show that the lowest-energy structures are dominated by central cores which correspond to the ground states of Mo n(n = 2,4,6,8,10) clusters and nitrogen atoms which surround these cores.The average binding energy,the adiabatic electron affinity(AEA),the vertical electron affinity(VEA),the adiabatic ionization potential(AIP) and the vertical ionization potential(VIP) of Mo2nNn(n=1-5) clusters have been estimated.The HOMO-LUMO gaps reveal that the clusters have strong chemical activities.An analysis of Mulliken charge distribution shows that charge-transfer moves from Mo atoms to N atoms and increases with cluster size.     

B$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;$lt;/sub$gt;Y($lt;i$gt;n$lt;/i$gt;=1–11)团簇的结构和电子性质

利用密度泛函理论TPSSh方法对B采用6-311+G(d), 对Y采用Lanl2dz相对论有效势基组, 研究了B_nY (n=1–11)团簇的平均结合能、二阶能量差分、最高分子占据轨道和最低空轨道之间的能级间隙、极化率和第一静态超极化率等物理化学性质. 结果表明, 随着尺寸的增大, B_nY (n=1–11)团簇的最低能量结构从平面逐步演变为立体结构. 随硼原子数n的增加, 团簇的平均结合能表明了较好的热力学稳定性, 有利于Y掺杂B团簇形成较大的块体材料.二阶能量差分表明基态B₃Y, B₅Y和B₇Y团簇较相邻团簇稳定. 能隙表明了基态B₃Y, B₅Y, B₇Y和B₉Y的化学稳定性较高. 综合说明B_nY (n=1–11)硼团簇中, 基态B₃Y, B₅Y和B₇Y具有较好的稳定性. 极化率表明基态B_nY团簇的电子结构随B原子的增加趋于紧凑, 第一静态超极化率表明基态B₅Y, B₄Y, B₃Y和B₆Y平面结构的团簇具有明显的非线性光学性质, 为寻找性能优异的非线性光学材料提供了一定的参考. 关键词： 密度泛函TPSSh方法 nY (n=1–')" href="#">B_nY (n=1– 11)团簇 几何结构 电子性质     

Density functional study of AunCu (n=1-7) clusters

The possible stable geometrical configurations and the relative stabilities of the lowest-lying isomers of copper-doped gold clusters,Au n Cu (n=1-7),are investigated using the density functional theory.Several low-lying isomers are determined.The results indicate that the ground-state Au n Cu clusters have planar structures for n=1-7.The stability trend of the Au n Cu clusters (n=1-7),shows that odd-numbered Au n Cu clusters are more stable than the neighbouring even-numbered ones,thereby indicating the Au 5 Cu clusters are magic cluster with high chemical stability.     

SimGen(m+n=9)团簇结构和电子性质的计算研究

硅锗团簇结构与电子性质的研究对于研发新型微电子材料具有重要意义. 将遗传算法和基于密度泛函理论的紧束缚方法相结合, 研究了Si_mGe_n(m+n=9)团簇的原子堆积结构和电子性质. 计算结果发现, Si_mGe_n(m+n=9) 团簇存在两种低能原子堆积稳定构型: 带小金字塔的五边形双锥堆积和带桥位Ge原子的四面体紧密堆积. 随着团簇内锗原子数目的逐渐增加, 两种堆积结构均出现明显的转变, 其中最低能量的几何结构由单侧带相邻双金字塔的五边形双锥结构转变为双侧带相邻单金字塔的五边形双锥结构. 随着原子堆积结构的变化, 团簇内原子电荷分布及电子最高占据轨道与电子最低未占据轨道的能隙随团簇内所含硅和锗元素组分的不同呈现出明显的差异.     

(HMgN3)n(n=1–5)团簇结构与性质的密度泛函理论研究

利用密度泛函理论在B3LYP/6-311G^*水平上对叠氮化合物(HMgN₃)_n(n=1–5)团簇各种可能构型进行了几何优化,预测了各团簇的最稳定结构. 并对最稳定结构的成键特性、电荷分布、振动特性及稳定性进行理论研究. 结果表明:HMgN₃团簇最稳定结构为直线型;(HMgN₃)_n(n=2,5)团簇最稳定结构为叠氮基中N原子和金属原子相连构成Mg–N–Mg结构;(HMgN₃)_n(n=3,4)团簇最稳定结构为叠氮基与Mg原子相互链接形成的环状结构. 团簇最稳定结构中金属Mg原子均显示正电性,H原子均显示负电性,叠氮基中间的N原子显示正电性、两端的N原子显示负电性,且与Mg原子直接作用的N原子负电性更强. Mg–N键和Mg–H键为典型的离子键,叠氮基内N原子之间是共价键. 团簇最稳定结构的红外光谱分为三部分,其最强振动峰均位于2258–2347 cm^-1,振动模式为叠氮基中N–N键的反对称伸缩振动. 叠氮基在团簇和晶体中结构不变,始终以直线型存在. 稳定性分析显示,(HMgN₃)₃团簇相对于其他团簇更为稳定. 关键词： 3)_n(n=1–5)团簇')" href="#">(HMgN₃)_n(n=1–5)团簇 叠氮基 密度泛函理论 结构与性质     

Equilibrium geometries and electronic properties of BenLi （n=2-15） clusters from first principles

This paper studies the equilibrium geometries and electronic properties of Ben and BenLi clusters, up to n=15, by using density-functional theory（DFT） at B3LYP/6-31G（d） level. The lowest-energy structures of Ben and BenLi clusters were determined. The results indicate that a single lithium impurity enhances the stability and chemical reactivity of the beryllium clusters. It finds that the geometries of the host clusters change significantly after the addition of the lithium atom for n ≥8. The lithium impurity prefers to be on the periphery of beryllium clusters, and occupies vertex sites. Both Be4Li, Be9Li, and Be13Li were found to be particularly stable with higher average binding energy, local peaks of second-order energy difference and fragmentation energies. For all the BenLi clusters studied, we found charge transfers from the Li to Be site and co-existence of covalent and metallic bonding characteristics.     

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     

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     

多参考组态相互作用方法计算研究XOn(X=S,Cl；n=0,±1)的解析势能函数和光谱常数

采用从头计算的多参考组态相互作用方法和含扩散基的3个基组aug-cc-PVXZ (X=D,T,Q) 计算了SO和ClO分子及其分子离子的势能曲线，确定了平衡几何结构、离解能，并采用Feller拟合递推方法得到了基函数为无穷大计算水平值. 确定了SO^－，ClO⁺，ClO^-分子离子的基态. 通过Murrell-Sorbie势能函数和最小二乘法拟合得到了解析势能函数. 基于所得的势能函数，通过解核运动的薛定谔方程得到振 关键词： 多参考组态相互作用 势能曲线 解析势能函数 光谱常数     

Photoreflectance and photoluminescence study of short period (GaAs)n/(AlAs)n superlattices with n = 1 – 15

Photoreflectance and photoluminescence measurements were performed in (GaAs)_n/(AlAs)_n (n = 1 – 15) short-period superlattices in the temperature range from 25 K to 275 K. Weak signals of photoreflectance associated with the critical point of the pseudodirect transition, weakly allowed direct transition arising from the zone-folding effect, have been observed as well as main signals associated with the direct allowed transitions. This assignment is supported by the measurement and analysis of the temperature dependence of the photoluminescence intensity.