Stability and electronic properties of Rh-doped ruthenium clusters and their interaction with NH3 molecule

The stability and electronic properties of the Rh-doped ruthenium clusters and their reactivity towards NH₃ molecule have been studied using DFT calculations with the BLYP-D3/SDD level of theory. The results show that the doping of Ru clusters with Rh atom improves the catalytic performances of pure Ru clusters, and the Ru₅Rh and Ru₇Rh clusters are assumed to be less reactive than their neighbours. The interaction of NH₃ with clusters exhibits that the Ru atoms are preferred adsorption sites for the NH₃ molecule, and the adsorption takes place between the Ru atom of clusters and the N atom of NH₃ molecule. The adsorption energies of NH₃ on Ru_nRh clusters are in the range of ?101.5 to ?218.4?kJ?mol^?1, suggesting a strong adsorption between both species. Upon adsorption process, the electronic properties of the Ru_nRh clusters were substantially changed. The variation of E_g (ΔE_g) for the Ru_nRh (n?≥?7) clusters is very important (ΔE_g?≥?55%), suggesting that these clusters are very sensitive to the NH₃ molecule. Hence, these clusters can be employed as nanosensors for the detection of the NH₃ gas.     

The relativistic density functional investigations on geometries, electronic and magnetic properties of Irn (n=1-13) clusters

<正>The Ir_n(n=1-13) clusters are studied using the relativistic density functional method with generalized gradient approximation.A series of low-lying structures with different spin multiplicities have been considered.It is found that all the lowest-energy Ir_n(n=4-13) geometries prefer non-compact structures rather than compact structure growth pattern.And the cube structure is a very stable cell for the lowest-energy Ir_n(n8) clusters.The second-order difference of energy,the vertical ionization potentials,the electron affinities and the atomic average magnetic moments for the lowest-energy Ir_n geometries all show odd-even alternative behaviours.     

Density functional investigation on the structures and properties of Li atom doped Au20 cluster

Structures and properties of an Au₂₀ cluster doped with two Li atoms, Au₁₈Li₂, have been investigated using relativistic density functional theory within the framework of the zeroth-order regular approximation. Various initial structures have been generated and employed for geometry optimization followed by vibration analysis to check the stability of the final optimized structures. We have calculated various properties like binding energy, ionization potential, electron affinity and the HOMO–LUMO gap of these structures. It has been found that two dopant Li atoms favour occupying two different surface positions of the pyramidal Au₂₀ cluster. The binding energy of the surface-doped Au₁₈Li₂ cluster is 1.017?eV higher than that of the pure Au₂₀ cluster and the HOMO–LUMO gap (1.742?eV) is as high as a pure Au₂₀ cluster (1.786?eV). Interestingly, we observe that the HOMO–LUMO gap as well as the binding energy can be increased beyond those of the Au₁₈Li₂ cluster with the help of further Li atom doping. In fact, a doped tetrahedral Au₁₆Li₄ cluster, where all the dopants are at the surface sites, possesses a very high HOMO–LUMO gap of 2.117?eV. Geometric and energetic parameters indicate that the Au₁₆Li₄ cluster might be considered as a possible ‘superatom’ in the design of novel cluster-assembled materials.     

Spin-polarised DFT study of cobalt-doped gallium clusters

The structural, electronic and magnetic properties of small gallium clusters doped with Cobalt have been studied using spin-polarised density functional theory. The binding energy per atom, second-order differences of total energies and fragmentation energies of equilibrium geometries of the host Ga_n+1 and doped Ga_nCo (n = 1–12) clusters are computed. Doped clusters are found to be more stable than pure Ga clusters; Ga₃Co, Ga₅Co and Ga₈Co clusters are exceptionally stable. Doping with Co changes the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO–LUMO) gap, and also affects the magnetic moments of clusters.     

Au_n(n=2—9)团簇的几何结构和电子特性

采用密度泛函DFT中的B3LYP方法 ,选择LANL2DZ基组 ,对Aun(n =2— 9)小团簇的各种可能结构进行优化 ,得到了它们的基态平衡结构并计算出其原子化能 .研究表明 :随着团簇尺寸的增大 ,单个原子的平均原子化能逐渐增大 .同时分析了团簇的能级分布、最高占据轨道与最低空轨道之间形成的能级间隙 .计算出了电子亲和能和电离势 ,计算值与实验值非常接近 .最后分析了费米能级、电子亲和能和电离势形成“奇 -偶”振荡效应的原因     

第一性原理对NaBen(n=1—12)团簇最低能量结构及其电子性质的研究

从第一性原理出发对NaBe_n(n=1—12)团簇的最低能量结构和电子性质进行了研究.结果表明，掺杂原子(Na)导致主团簇Be_n的几何结构发生显著变化；出现了共价键和金属键的成键特性；Na-Be最近邻间距和能隙随着团簇尺寸的增加出现了振荡;n=4是团簇的幻数. 关键词： n团簇')" href="#">NaBe_n团簇 最低能量结构 电子性质     

BenLa (n=1—18) 团簇的结构、电子性质和磁性

采用基于密度泛函理论的第一性原理方法,在多种初始构型下充分考虑自旋多重度,研究了Be_nLa团簇的平衡几何结构、电子性质和磁性.结果表明：Be_nLa团簇的基态附近有许多能量非常接近的同分异构体,说明该团簇结构较复杂,对其基态的寻找极具挑战性.Be_nLa团簇具有磁性且稳定性远高于Be_n+1团簇,由此可知通过选择合适的掺杂元素可能得到高稳定性的磁性团簇.Be_{1 关键词： n}La团簇')" href="#">Be_nLa团簇 平衡几何结构 电子性质和磁性     

Structural, electronic and magnetic properties of ConRh (n=1-8) clusters from density functional calculations

The geometries, stabilities, electronic and magnetic properties of Co_nRh (n=1-8) clusters have been investigated systematically within the framework of the generalized gradient approximation density-functional theory. The results indicate that the most stable structures of Co_nRh (n=1-8) clusters are all similar to those of corresponding Co_n+1 clusters. Maximum peaks of second-order energy difference are found at n=2, 4 and 7, indicating that these clusters possess relatively higher stability than their respective neighbors. The magnetism of the ground state of alloy clusters all displays ferromagnetic coupling except for Co₃Rh. In addition, the doped Rh atom exhibits an important influence on the magnetism of alloy clusters, e.g., compared with corresponding pure Co_n clusters, the local moment of Co atom is noticeably enhanced in Co_nRh alloy clusters at n=1, 2, 5, 6, 7 and 8, while reduced at n=3 and 4. Further analysis based on the average bond length, the charge transfer and the spin polarization has been made to clarify the different magnetic responses to Rh doping.     

密度泛函理论研究CO与Nin（n=1—6）团簇的相互作用

采用密度泛函理论对CO吸附在镍团簇表面进行了系统研究.结果表明,Ni_nCO团簇的最低能量结构是在Ni_n团簇最低能量结构的基础上吸附CO生长而成,CO的吸附没有改变Ni_n团簇的结构;CO分子在Ni_n团簇表面发生的是非解离性吸附,与优化的CO键长（0.1138?nm）相比,吸附后C—O键长变长（0.1180—0.1214?nm）,表明吸附后C—O键被削弱,CO分子被活化.自然键轨道分析表明,CO分子只与最近邻的Ni原子发生相互作用;CO分子与Ni原子相互作用的本质是CO分子内的杂化轨道与Ni原子3d, 4s, 4p轨道相互作用的结果. 关键词： nCO团簇')" href="#">Ni_nCO团簇 n团簇')" href="#">Ni_n团簇 平衡结构 电子性质     

第一性原理对GenB(n=12—19)团簇的最低能量结构及其电子性质的研究

利用第一性原理在广义梯度近似下，研究了Ge_nB(n=12—19)团簇的结构和电子性质. 结果表明：Ge_nB(n=12—19)团簇具有较大的能隙;这些团簇的最低能量结构包含有Ge₉或Ge₁₀结构单元；B原子嵌套在Ge_n团簇中和B原子替代Ge_n+1团簇的Ge原子是构成Ge_{n 关键词： n}B团簇')" href="#">Ge_nB团簇 最低能量结构 电子性质     

Structural,electronic,optical,and magnetic properties of Co-doped Cu_2O

We investigate the magnetic properties of Co-doped Cu_2O. We studied first the electronic and structural properties of Cu_2O using the optimization of the lattice constant which is 4.18 . The calculated gap is found between 0.825 eV and1.5 eV, these values are in good agreement with the experimental results. The Co atoms are inserted in Cu_2O by means of the density functional theory(DFT) using LSDA, LSDA +U, and LSDA + MBJ approximations in the WIEN2 k code, based on the supercell model by setting up 12, 24, and 48 atoms in(1×1 × 2),(1 × 2 × 2), and(2 × 2×2) supercells respectively with one or two copper atoms being replaced by cobalt atoms. The energy difference between the ferromagnetic and antiferromagnetic coupling of the spins located on the substitute Co has been calculated in order to obtain better insight into the magnetic exchange coupling for this particular compound. The studied compound exhibits stable integer magnetic moments of 2 μBand 4 μBwhen it is doped with 2 atoms of Co. Optical properties have also been worked out. The results obtained in this study demonstrate the importance of the magnetic effect in Cu_2O.     

SinMn (n=2--14) 的结构和电子性质

采用密度泛函理论对SinMn (n=2--14)的几何结构和电子性质进行了研究,结果表明,从Si12Mn 团簇开始,Mn原子陷入了Si原子形成的笼内;二阶能量差分,分裂能和垂直电离势都表明5,10,12是团簇的幻数,其中Si12Mn团簇是最稳定的;在所研究的团簇中,Si5Mn团簇中Mn原子的磁矩是最大的(3.923uB);Mn 原子的4s, 3d 和Si原子的3s, 4p的较强杂化是导致Mn原子磁矩减小的原因;当n ≥7时,SinMn团簇的总磁矩是1 uB.     

Structure, electronic and magnetic properties of Ca-doped chromium oxide studied by the DFT method

Using first-principles density functional theory calculations within the generalised gradient approximation (GGA) as well as GGA+U method we study Ca-doped α-Cr₂O₃ crystal. Structural, electronic and magnetic properties due to the singular impurity incorporation have been investigated and discussed in detail. Atomic shifts as well as computed Bader charges on atoms imply the importance of ionic nature in the atomic interactions in chromium oxide. The study improves our knowledge on how the crystalline lattice reacts on the presence of a Ca dopant. According to our research it is found that Ca impurity incorporation produces some local changes upon the electronic band structure of the material without occurrence of local states within the band-gap. It is found that Ca incorporation produces change in magnetic behaviour of the crystal: it becomes ferromagnetic.     

Geometries, stabilities, and electronic properties of Be-doped gold clusters: a density functional theory study

We have systematically investigated the geometrical structures, relative stabilities and electronic properties of small bimetallic AunBe (n = 1, 2, . . . , 8) clusters using a density functional method at BP86 level. The optimized geometries reveal that the impurity beryllium atom dramatically affects the structures of the Aun clusters. The averaged binding energies, fragmentation energies, second-order difference of energies, the highest occupied-lowest unoccupied molecular orbital energy gaps and chemical hardness are investigated. All of them exhibit a pronounced odd-even alternation, manifesting that the clusters with even number of gold atoms possess relatively higher stabilities. Especially, the linear Au2Be cluster is magic cluster with the most stable chemical stability. According to the natural population analysis, it is found that charge-transferring direction between Au atom and Be atom changes at the size of n = 4.     

Geometrical, electronic, and magnetic properties of small AunSc (n=1-8) clusters

Geometrical, electronic, and magnetic properties of the Sc-doped gold clusters, Au_nSc (n=1-8), have been studied using the density-functional theory within the generalized gradient approximation. An extensive structural search shows that the Sc atom in low-energy Au_nSc isomers tends to occupy the most highly coordinated position. The substitution of a Sc atom for an Au atom in the Au_n+1 cluster markedly changes the structure of the host cluster. Moreover, we confirm that the ground-state Au₆Sc cluster has a distortion to a lower D_2h symmetry. The relative stabilities and electronic properties of the lowest-energy Au_nSc clusters are analyzed based on the averaged binding energies, second-order energy differences, fragmentation energies, chemical hardnesses, and HOMO-LUMO gaps. It is found that the magic Au₃Sc cluster can be perceived as a superatom with high chemical stability and its HOMO-LUMO gap is larger than that of the closed-shell Zr@Au₁₄ cluster. The high symmetry and spin multiplicity of the Au₃Sc and Au₆Sc clusters are responsible for their large vertical ionization potential and electron affinity. The magnetism calculations indicate that the magnetic moment of the Sc atom in the ground-state Au_nSc (n=2-8) clusters gradually decreases for even n and is completely quenched for odd n.     

密度泛函理论研究ScnO(n=1—9)团簇的结构、稳定性与电子性质

采用基于密度泛函理论的BP86/CEP-121G （O原子采用6-311G^**基组）方法,对Sc_nO （n=1—9）团簇的几何结构、能量与稳定性、电子结构性质及其随团簇尺寸的变化趋势进行了研究.随着团簇原子个数的增加,O原子从位于Sc_n团簇结构的边缘转变为占据团簇的内部位置.O原子的掺入增加了Sc_n团簇的稳定性,使其能隙升高,并改变了其稳定性及电子结构性质随团簇尺寸变化的规律;含有偶数个Sc原子的氧化物团簇比其周围邻近的含有奇数个Sc原子的氧化物团簇具有相对较高的稳定性.Sc_nO团簇电离势的理论计算值与实验值符合得较好,而其电子亲和势呈现振荡交替上升的变化趋势;用最大化学硬度规律等方法表征了Sc_nO氧化物团簇的稳定性和电子结构性质. 关键词： nO团簇')" href="#">Sc_nO团簇 几何结构 电子性质 密度泛函理论     

Structural and electronic properties of full range of ternary PtmAunAgl (m + n+l = 5, 6 and 7) clusters: a density functional theory investigation

ABSTRACT

Density functional theory calculations have been carried out on ternary Pt_mAu_nAg_l clusters of low nuclearity (m?+?n+l?=?5, 6 and 7). Various properties including average bond distance, binding energy, mixing energy, ionisation potential, electron affinity, HOMO–LUMO gap and fragmental channel, are reported for the optimised structures. The variations of the calculated properties of the Pt_mAu_nAg_l clusters as a function of concentrations (i.e. all m-, n-, and l-values) are displayed by ternary diagrams. The geometric, energetic and electronic properties are sensitive to the composition and size of Pt_mAu_nAg_l clusters.     

密度泛函理论对AunSc3(n=1—7)团簇结构和性质的研究

采用密度泛函理论中的广义梯度近似(GGA)对Au _{n Sc3(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,与纯金团簇相比,AunSc3 较早出现了立体结构,三角双锥结构的Au2Sc3是AunSc3(n>2)团簇生长的基元;Sc原子的掺杂提高了增强了Au 关键词： n} Sc₃团簇')" href="#">Au_n Sc₃团簇 几何结构 电子性质     

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).     

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.