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1.
Geometrical, electronic, and magnetic properties of the Sc-doped gold clusters, AunSc (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 AunSc isomers tends to occupy the most highly coordinated position. The substitution of a Sc atom for an Au atom in the Aun+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 D2h symmetry. The relative stabilities and electronic properties of the lowest-energy AunSc 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 AunSc (n=2-8) clusters gradually decreases for even n and is completely quenched for odd n.  相似文献   

2.
The structures, stabilities and electronic properties of FePbn (n=1-14) clusters have been studied using the density-functional theory (DFT). Extensive search of the ground-state structures has been carried out by considering a larger number of structural isomers for each cluster size. The Fe atom gradually falls into the interior of the Pb framework as the number of Pb atom increases from 1 to 14. The FePbn clusters at n=3, 5, 10, 12 have relatively higher stability by analyzing the averaged binding energy and the second-order energy difference. Especially, FePb12 is more stable, owing to its highest symmetrical icosahedron structure. The magnetic moments of FePbn clusters do not quench when Fe atom is encapsulated in the Pb framework and mostly originate from 3d state of Fe atom.  相似文献   

3.
郭平  郑继明  赵佩  郑琳琳  任兆玉 《中国物理 B》2010,19(8):83601-083601
<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.  相似文献   

4.
吕瑾  秦健萍  武海顺 《物理学报》2013,62(5):53101-053101
采用密度泛函理论中的广义梯度近似(DFT-GGA)对ConAl (n= 1–8)合金团簇进行了系统的几何、 电子结构和磁性质研究. 研究结果表明Al原子倾向于与Co原子形成最大的成键数, 即Al原子均处在团簇原子拥有最大配位数的位置上. Al掺杂后ConAl团簇的稳定性减弱, 磁性降低. 磁性降低的幅度与实验上对较大ConAlM团簇的磁性检测结果获得了很好地符合. 在所有ConAl团簇的最稳定结构中, 除Co4Al外, Al与近邻Co原子均呈现反铁磁性耦合. 相对于纯Co团簇,非磁性Al元素的掺入以及Al掺杂后Co原子整体自旋极化的减弱 是导致ConAl团簇磁性的降低主要原因. 关键词: nAl合金团簇')" href="#">ConAl合金团簇 几何结构 磁性 自旋极化  相似文献   

5.
Ab-initio calculations are performed to investigate the structural, electronic and magnetic properties of spin-polarized diluted magnetic semiconductors composed of II-VI compounds Cd1−xCoxX (X=S, Se, Te) at x=0.25. From the calculated results of band structure and density of states, the half-metallic character and stability of ferromagnetic state for Cd1−xCoxS, Cd1−xCoxSe and Cd1−xCoxTe alloys are determined. It is found that the tetrahedral crystal field gives rise to triple degeneracy t2g and double degeneracy eg. Furthermore, we predict the values of spin-exchange splitting energies Δx(d) and Δx(pd) and exchange constants N0α and N0β produced by the Co 3d states. Calculated total magnetic moments and the robustness of half-metallicity of Cd1−xCoxX (X=S, Se, Te) with respect to the variation in lattice parameters are also discussed. We also extend our calculations to x=0.50, 0.75 for S compounds in order to observe the change due to increase in Co.  相似文献   

6.
The structural and electronic properties of Bin (n = 2-14) clusters have been systematically studied using gradient-corrected density-functional theory. For each cluster size, a number of structural isomers were constructed and optimized to search for the lowest-energy structure. The competition of several structural patterns such as cages, superclusters, and layered structures leads to the alternating appearance of these configurations as global minima. Although the tendency of Bi to form puckered-layer structures is already well-known, the electronic states of Bin clusters are still far from that of the bulk. As well, a remarkable even-odd atom number oscillation is observed in the structural and electronic properties of the clusters, implying that the stability of Bin clusters is mainly dominated by the electron shell effect rather than by geometrical packing. The theoretically calculated values for electron affinities agree well with available experimental data.  相似文献   

7.
田付阳  王渊旭  井群  田凯  罗有华 《物理学报》2008,57(3):1648-1655
利用密度泛函理论(DFT)的B3PW91方法,在6-311G水平上对BMgn,AlMgn(n=1—12)团簇进行了几何结构优化和电子性质分析. 发现随着原子个数的增加, B原子进入镁团簇的内部, 而AlMgn和镁团簇有相似的生长模式. B,Al原子的掺杂均能使镁团簇的平均结合能增大,稳定性增强, BMgn,AlMgn关键词: 密度泛函理论 最低能量结构 n和AlMgn团簇')" href="#">BMgn和AlMgn团簇 NBO电荷布居  相似文献   

8.
基于第一性原理,利用密度泛函理论中的广义梯度近似 (GGA)对GenFe(n=1—8)团簇进行了结构优化、能量及频率的计算,得到了 GenFe(n=1—8)团簇在不同自旋多重度下的平衡构型及其基态结构.结果表明:GenFe混合团簇的平均结合能明显比相应纯锗团簇的平均结合能有所增大,即掺杂Fe原子可以提高锗团簇的稳定性;纯锗团簇的基态除了Ge2为自旋三重态外其他均为单重态,而混合团簇GenFe(n=1—8)的基态均为自旋三重态;对GenFe(n=1—8)团簇的磁性做了较系统的研究,发现团簇总磁矩随团簇尺寸增大基本稳定在2μB (只有Ge8Fe的总磁矩2.391μB较明显地偏离了2μB),另外团簇中Fe原子的磁矩在2.5μB左右振荡. 关键词nFe团簇')" href="#">GenFe团簇 密度泛函理论(DFT) 自旋多重度 磁矩  相似文献   

9.
葛桂贤  闫红霞  井群  张建军 《物理学报》2011,60(3):33101-033101
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="#">Aun Sc3团簇 几何结构 电子性质  相似文献   

10.
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ScnO (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Scn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Scn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.ScnO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ScnO氧化物团簇的稳定性和电子结构性质. 关键词nO团簇')" href="#">ScnO团簇 几何结构 电子性质 密度泛函理论  相似文献   

11.
Structural, electronic properties and relative stability of quasi-two-dimensional (2D) free-standing planar nano-block (NBs) structures Tin+1Al0.5Cn and Tin+1Cn (n = 1 and 2), which can be prepared using the recently developed procedure of exfoliation of corresponding NBs from MAX phases, were examined within first principles calculations in comparison with parent MAX phases Ti3AlC2 and Ti2AlC. We found that in general Tin+1Cn and Tin+1Al0.5Cn NBs retain the atomic geometries of the corresponding blocks of the MAX phases, but some structural distortions for the NBs occur owing to the lowering of the coordination number for atoms in the external Ti sheets of the nano-block structures. Our analysis based on their cohesive and formation energies reveals that the stability of the nano-block structures increases with index n (or, in other words, with a growth of the number of Ti–C bonds), the Al-containing NBs becoming more stable than the “pure” Ti–C NBs. Our data show that the magnetization of the simulated planar nano-block structures can be expected; so, for the Ti3C2 nano-block the most stable will be the spin configuration, where within each external Ti sheet the spins are coupled ferromagnetically together with antiferromagnetic ordering between opposite external titanium sheets of this nano-block.  相似文献   

12.
The host Gan+1 and doped GanNb (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 (Eb/atom), second-order differences of total energies (Δ2E), fragmentation energies (Ef) and HOMO-LUMO gaps of Gan+1 and GanNb (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 GanNb cluster size increases. Besides, the doping of Nb atom also brings the decrease as the cluster sizes increases for atomic spin magnetic moments (μb).  相似文献   

13.
从第一性原理出发对NaBen(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Ben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="#">NaBen团簇 最低能量结构 电子性质  相似文献   

14.
温俊青  夏涛  王俊斐 《物理学报》2014,63(2):23103-023103
采用密度泛函理论方法,在BPW91/LANL2DZ水平下详细研究了Pt n Al(n=1—8)团簇的几何结构、稳定性和电子性质.同时,分析了团簇的结构演化规律、平均结合能、二阶能量差分、能隙、磁性、Mulliken电荷和电极化率.结果表明:除Pt2Al外,所有Pt n Al(n=1—8)团簇的基态几何结构都可以用Al原子替换Pt n+1基态构型中的Pt原子得到,且Al原子位于较高的配位点上.二阶能量差分、能隙的分析结果表明,PtAl和Pt4Al团簇相对其他团簇具有较高的稳定性.Mulliken电荷分析表明,Al原子所带的电荷转移到Pt原子上,Al原子是电荷的捐赠者.磁性的分析说明,单个Al原子的加入对Pt n团簇的平均每原子磁矩随尺寸的变化趋势没有影响,但总体上降低了Pt n团簇的平均磁矩.极化率的研究表明,富Pt团簇的非线形光学效应强,容易被外场极化.  相似文献   

15.
采用密度泛函理论中的广义梯度近似(GGA)对CoBen(n=1—12)团簇的几何构型进行优化,并对能量、频率和磁性进行了计算,同时考虑了电子的自旋多重度.得到了CoBen(n=1—12)团簇最低能量结构的自旋多重度是2和4.在CoBen(n=1—12)团簇中,Co原子的磁矩出现了奇偶振荡,当n=6时,Co原子的4s,3d和Be原子的2s,2p较强杂化、Co-Be键长的减小以及对称性的降低导致Co原子的磁矩最小.通过对CoBen(n=1—12)团簇电子性质的分析,得出了掺杂可以增强团簇稳定性和有利于增加合金化学活性的结论.n=5,10是团簇的幻数. 关键词n团簇')" href="#">CoBen团簇 自旋多重度 磁矩 电子性质  相似文献   

16.
A series of rare-earth doped BiFeO3 samples, Bi1−xRxFeO3 (x=0-1, R=La, Nd, Sm, Eu and Tb), were prepared in this work. X-ray diffraction analysis showed that the structure of rare-earth doped BiFeO3 was transformed from rhombohedral lattice to orthorhombic one by increasing x. The lattice constants and unit-cell volume decreased with the increasing of the doping content, while both the Néel temperature and magnetization were enhanced. A magnetic phase transition was observed at about 35 K for BiFeO3. The variation of the magnetization with temperature depended on applied field strength and magnetizing history, which was explained according to the antiferromagnetic exchange interaction between Fe and R sites in Bi1−xRxFeO3(x>0). The magnetocrystalline anisotropy contributed by Fe sublattice gave rise to a large coercivity in BixNd1−xFeO3 with an orthorhombic structure.  相似文献   

17.
The structural, electronic and magnetic properties of TMGen (TM=Mn, Co, Ni; n=1-13) have been investigated using spin polarized density functional theory. The transition metal (TM) atom prefers to occupy surface positions for n<9 and endohedral positions for n≥9. The critical size of the cluster to form endohedral complexes is at n=9, 10 and 11 for Mn, Co and Ni respectively. The binding energy of TMGen clusters increases with increase in cluster size. The Ni doped Gen clusters have shown higher stability as compared to Mn and Co doped Gen clusters. The HOMO-LUMO gap for spin up and down electronic states of Gen clusters is found to change significantly on TM doping. The magnetic moment in TMGen is introduced due to the presence of TM. The magnetic moment is mainly localized at the TM site and neighbouring Ge atoms. The magnetic moment is quenched in NiGen clusters for all n except for n=2, 4 and 8.  相似文献   

18.
Equilibrium geometries, relative stabilities, and magnetic properties of small AunMn (n=1-8) clusters have been investigated using density functional theory at the PW91P86 level. It is found that Mn atoms in the ground state AunMn isomers tend to occupy the most highly coordinated position and the lowest energy structure of AunMn clusters with even n is similar to that of pure Aun+1 clusters, except for n=2. The substitution of Au atom in Aun+1 cluster by a Mn atom improves the stability of the host clusters. Maximum peaks are observed for AunMn clusters at n=2, 4 on the size dependence of second-order energy differences and fragmentation energies, implying that the two clusters possess relatively higher stability. The HOMO-LUMO energy gaps of the ground state AunMn clusters show a pronounced odd-even oscillation with the number of Au atoms, and the energy gap of Au2Mn cluster is the biggest among all the clusters. The magnetism calculations indicate that the total magnetic moment of AunMn cluster, which has a very large magnetic moment in comparison to the pure Aun+1 cluster, is mainly localized on Mn atom.  相似文献   

19.
The geometrical structures, relative stabilities, and electronic properties of bimetallic AunMg (n=1-8) clusters have been systematically investigated by means of first-principle density functional theory. The results show that the ground-state isomers have planar structures for n=1-7. Here, the calculated fragmentation energies, the second-order difference of energies, the highest occupied-lowest unoccupied molecular orbital energy gaps, and the hardness exhibit a pronounced odd-even alternation, manifesting that the clusters, especially Au2Mg, with even-number gold atoms have a higher relative stability. On the basis of natural population analysis, the charge transfer and magnetic moment are also discussed.  相似文献   

20.
Un-hydrogenated and hydrogenated Cu, Co co-doped ZnO (Zn0.96−xCo0.04CuxO, x=0.03, 0.04 and 0.05) nanopowders have been synthesized by co-precipitation method. The synthesized samples have been characterized by powder X-ray diffraction, energy dispersive X-ray spectra, UV–Visible spectrophotometer and Fourier transform infrared spectroscopy. The calculated average crystalline size increases from 37.3 to 50.6 nm for un-hydrogenated samples from x=0.03 to 0.05 and it changes from 29.4 to 34.9 nm for hydrogenated samples. The change in lattice parameters, micro-strain, a small shift of X-ray diffraction peaks towards lower angles and reduction in energy gap reveal the substitution of Cu2+ ions into Zn–Co–O lattice. The hydrogenation effect reduces the particle size and induces the more uniform distribution of particles than the un-hydrogenated samples which is confirmed by SEM micrographs. Photoluminescence spectra of Zn0.96−xCo0.04CuxO system shows that red shift in near band edge ultraviolet emission from 393 to 403 nm with suppressing intensity and a blue shift in green band emission from 537 to 529 nm with enhancing intensity confirms the substitution of Cu into the Zn–Co–O lattice.  相似文献   

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