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Ali Sebetci 《Journal of magnetism and magnetic materials》2012,324(4):588-594
The structural, energetic, electronic and magnetic properties of small bimetallic ConPtm (n+m≤5) nanoalloy clusters are investigated by density functional theory within the generalized gradient approximation. A plausible candidate for the ground state isomer and the other possible local minima, binding energies, relative stabilities, magnetic moments, the highest occupied and the lowest unoccupied molecular orbital energy gaps have been calculated. It is found as a general trend that average binding energies of Co-Pt bimetallic clusters increase with Pt doping. Planar structures of pure Co clusters become 3D with the addition of Pt atoms. CoPt2, Co2Pt2, Co3Pt2, and CoPt4 nanoalloys are identified as the most stable species since they have higher second finite difference in energy than the others. Pt doping decreases the total spin magnetic moment gradually. A rule for the prediction of the total spin moments of small Co-Pt bimetallic clusters is derived. 相似文献
3.
An all-electron scalar relativistic calculation on AunH2S (n = 1-13) clusters has been performed by using density functional theory with the generalized gradient approximation at PW91 level. The small gold cluster would like to bond with sulfur in the same plane and the H2S molecule prefers to occupy the on-top and single fold coordination site in the cluster. The Aun structures and H2S molecule in all AunH2S clusters are only slightly perturbed and still maintain their structural integrity. After adsorption, the S-H, H-H bond-lengths and most Au-Au bond-lengths are elongated, only a few Au-Au bond-lengths far from H2S molecule are shortened. The reactivity enhancement of H2S molecule is obvious and the strong gold-sulfur bond is observed expectedly. The most favorable adsorption takes place in the case that the H2S molecule is adsorbed by an even-numbered Aun cluster and becomes AunH2S cluster with even number of valence electrons. It is believed that the strong scalar relativistic effect is favorable to H2S molecule adsorption onto small gold clusters and is also one of the important reasons for the strong gold-sulfur bond. 相似文献
4.
S. Dennler J. L. Ricardo-Chavez J. Morillo G. M. Pastor 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):237-240
Structural and magnetic properties of small bimetallic
clusters like
CoMRhN,
NiNaN, and NiCuN
are determined in the framework of a generalized
gradient-corrected approximation to density functional theory.
The role of magnetism on the most stable structure and on the
energy differences among the low-lying isomers is quantified by
comparing magnetic and non-magnetic solutions of the Kohn-Sham
equations. The correlation between structure, chemical order,
and environment-dependent magnetic properties is discussed. 相似文献
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6.
Density functional study on structural and electronic properties of bimetallic gold--yttrium clusters: comparison with pure gold and yttrium clusters 下载免费PDF全文
Employing first-principles methods, based on the density functional
theory, this paper investigates the ground state geometric and
electronic properties of pure gold clusters, pure yttrium clusters
and gold clusters doped each with one yttrium atom. It is shown that
the average bond lengths in the Augold--yttrium bimetallic cluster,
density functional theory, HOMO--LUMO gap, equilibrium structure Project supported by the Education
Committee of Chongqing (Grant No KJ051105) and the National Natural
Science Foundation of China (Grant
No 10276028). 3640, 3640B, 3120A, 3130J 9/1/2007 12:00:00 AM Employing first-principles methods, based on the density functional
theory, this paper investigates the ground state geometric and
electronic properties of pure gold clusters, pure yttrium clusters
and gold clusters doped each with one yttrium atom. It is shown that
the average bond lengths in the Augold--yttrium bimetallic cluster,
density functional theory, HOMO--LUMO gap, equilibrium structure Project supported by the Education
Committee of Chongqing (Grant No KJ051105) and the National Natural
Science Foundation of China (Grant
No 10276028). 3640, 3640B, 3120A, 3130J 9/1/2007 12:00:00 AM Employing first-principles methods, based on the density functional
theory, this paper investigates the ground state geometric and
electronic properties of pure gold clusters, pure yttrium clusters
and gold clusters doped each with one yttrium atom. It is shown that
the average bond lengths in the Au$_{n - 1}$Y($n \le $9) bimetallic
clusters are shorter than those in the corresponding pure gold and
yttrium clusters. The most stable isomers of the yttrium-doped gold
clusters tend to equally delocalize valence s, p and d electrons of
the constituent atoms over the entire structure. The Y atom has
maximum number of neighbouring Au atom, which tends to be
energetically favourable in the lowest-energy equilibrium structures,
because the Au--Y bond is stronger than the Au-Au bond. The
three-dimensional isomers of Au$_{n - 1}$Y structures are found in an
early appearance starting at $n$=5 (Au$_{4}$Y). Calculated vertical
ionization potential and electron affinities as a function of the
cluster size show odd-even oscillatory behaviour, and resemble pure
gold clusters. However, one of the most striking feature of pure
yttrium clusters is the absence of odd-even alternation, in agreement
with mass spectrometric observations. The HOMO--LUMO gap of Au$_{3}$Y
is the biggest in all the doped Au$_{n - 1}$Y($n \le $9) bimetallic
clusters. 相似文献
7.
采用密度泛函理论与周期性平板模型相结合的方法,对HCOOH在Pd(111)表面top,fcc,hcp,bridge四个吸附位和Pd-Fe(111)表面Pd-top,Fe-top,PdPd-bridge,PdFe-bridge,FeFe-bridge,Pd2Fehcp,PdFe2-hcp,Pd2Fe-fcc,PdFe2-fcc等9个吸附位的13种吸附模型进行了能量计算、构型优化,得到了HCOOH较有利的吸附位;并对清洁表面进行能带分析.结果表明:掺杂Fe后,Pd催化剂对HCOOH催化活性增强;HCOOH在Pd(111)表面的最稳定吸附位fcc的吸附能是-41.8kJ·mol-1,在Pd-Fe(111)表面的最稳定吸附位Pd2Fe-hcp的吸附能是-126.5kJ·mol-1,而且HCOOH在金属表面属于化学吸附. 相似文献
8.
采用密度泛函理论与周期性平板模型相结合的方法,对HCOOH在Pd(111)表面top, fcc, hcp, bridge 四个吸附位和Pd-Fe(111)表面Pd-top, Fe-top, PdPd-bridge, PdFe-bridge, FeFe-bridge, Pd2Fe-hcp, PdFe2-hcp, Pd2Fe –fcc, PdFe2-fcc等9个吸附位的13种吸附模型进行了能量计算、构型优化,得到了HCOOH较有利的吸附位;并对清洁表面进行能带分析。结果表明:掺杂Fe后,Pd催化剂对HCOOH催化活性增强;HCOOH在Pd(111)表面的最稳定吸附位fcc的吸附能是-41.8kJ•mol-1,在Pd-Fe(111)表面的最稳定吸附位Pd2Fe-hcp的吸附能是-126.5 kJ•mol-1,而且HCOOH在金属表面属于化学吸附。 相似文献
9.
The equilibrium geometries and electronic properties of AunAl,
up to n=13, have been systematically investigated using the density
functional theory. The results show that, for the AunAl
clusters, two patterns are identified. Pattern one (n=2, 3, 8),
the lowest-energy geometries prefer two-dimensional structures.
Pattern two (n=4-7, 9--13), the lowest-energy geometries prefer
three-dimensional structures. According to the analysis of the
binding energy and the fragmentation energy, AunAl clusters
with odd n are found to be more stable than those with even n.
The same trend of alternation can be illuminated according to the
computational results in the HOMO--LUMO gap, the ionization
potential, and the electron affinities. The Al atom not only changes
the structures of pure gold clusters, but also enhances their
stabilities. NBO analysis indicates 6s orbital of Au atom hybridizes
with 3p orbital of Al atom. 相似文献
10.
This paper studies the small molybdenum clusters of Mon (n=2--8) and their adsorption of N2 molecule by using the density functional theory (DFT) with the generalized gradient approximation. The optimized structures of Mon clusters show the onset of a structural transition from a close-packed structure towards a body-centred cubic structure occurred at n=7. An analysis of adsorption energies suggests that the Mo2 is of high inertness and Mo6 cluster is of high activity against the adsorption of N2. Calculated results indicate that the N2 molecule prefers end-on mode by forming a linear or quasi-linear structure Mo--N--N, and the adsorption of nitrogen on molybdenum clusters is molecular adsorption with slightly elongated N--N bond. The electron density of highest occupied molecular orbital and lowest unoccupied molecular orbital, and the partial density of states of representative cluster are also used to characterize the adsorption properties of N2 on the sized Mon clusters. 相似文献
11.
L. A. Pérez X. López-Lozano I. L. Garzón 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,52(1-3):123-126
The adsorption of the cysteine amino acid (H–SCβH2–CαH–NH2–COOH) on the Au55 cluster is investigated through density functional theory calculations. Two isomers, with icosahedral (Ih) and chiral (C1) geometries, of the Au55 cluster are used to calculate the adsorption energy of the cysteine on different facets of these isomers. Results, only involving the S(thiolate)-Au bonding show that the higher adsorption energies are obtained when the sulfur atom is bonded to an asymmetrical bridge site at the facet containing Au atoms with the lowest coordination of the C1 cluster isomer. 相似文献
12.
Using density functional theory (DFT) calculations with an on-site Coulomb repulsion term, we study the composition, stability, and electronic properties of the most common FeOOH surfaces goethite(101), akaganeite(100), and lepidocrocite(010), and their interaction with water. Despite the differences in surface structure, the trends in surface stability of these FeOOH polymorphs exhibit remarkable similarities. We find that the reactivity and the binding configuration of adsorbates depend strongly on the coordination of surface iron: at the fourfold coordinated Fe2 site water is chemisorbed, whereas at the fivefold coordinated Fe1 water is only loosely bound with hydrogen pointing towards the surface. Our results show that the oxidation state of surface iron can be controlled by the surface termination where ferryl (Fe4 +) species emerge for oxygen terminated surfaces and ferrous iron (Fe2 +) at iron and water terminations leading to a reduced band gap. In contrast, the fully hydroxylated surfaces, identified as stable surface configurations at standard conditions from the surface phase diagram, show electronic properties and band gaps closest to bulk FeOOH with ferric surface iron (Fe3 +). Only in the case of goethite(101), a termination with mixed surface hydroxyl and aquo groups is stabilized. 相似文献
13.
锑烯(antimonene)是继石墨烯和磷烯之后出现的新型二维材料,在锂离子电池等领域受到关注.本文基于第一性原理的密度泛函理论,计算研究了锑烯对Li原子的吸附特性,包括Li原子的最稳定吸附构型、吸附密度以及吸附Li原子的扩散路径.结果表明:Li原子最稳定的吸附位置位于谷位,即底层Sb原子之上、顶层三个Sb原子中心位置,吸附能为1.69 eV,吸附距离为2.81?;能带计算发现,锑烯为带隙宽度1.08 eV的间接带隙半导体,吸附Li原子后费米能级上升进入导带,呈现出金属性;原子分波态密度分析发现, Sb原子的p电子态和Li原子的p和s电子态形成明显的共振交叠,表现出杂化成键的特征;随着吸附Li原子数量增加,锑烯晶格结构和电子结构发生较大变化.通过微动弹性带方法计算发现, Li原子在锑烯表面的扩散势垒为0.07 eV,较小的势垒高度有利于快速充放电过程. 相似文献
14.
T.T.P. Cheung 《Surface science》1984,140(1):151-164
X-ray photoemission of the Pt(4f) and Pd(3d) core-levels of small Pt and Pd metal clusters have been investigated. As cluster size decreases, there is a reduction in the lineshape asymmetry, a broadening in the linewidth, and a shift of the core-level toward the higher binding energies. The changes in the linewidth and line asymmetry can be interpreted in terms of the final state effects — the changes in the response of the valence electrons to the core-hole as a function of the cluster size. The decrease in the lineshape asymmetry is due to the reduction in the low-energy electron-hole screening and the linewidth broadening is due to the damping of the plasmons by the boundary surface of the cluster. 相似文献
15.
本文基于密度泛函理论(DFT)的第一性原理研究了苯并三氮唑(BTA)分子吸附于铜表面的反应活性特征及其吸附在三种不同取向晶面时的电荷转移以及成键情况,结果表明:BTA分子的亲电和亲核活性中心为N(1)、N(2)和C(5),在铜表面垂直吸附时为化学吸附,Cu原子的最外层价电子转移到N(2)原子上,两者形成配位键;BTA分子在三种不同取向的铜表面吸附时的吸附能大小为:Cu(110)x>Cu(100)x>Cu(111)x(x=T、B、H),T表示顶位,B表示桥位,H表示空位;BTA吸附在Cu(111)面的转移电荷量:T(顶位)>B(桥位)>H(空位). 相似文献
16.
采用密度泛函理论方法B3P86/6-31++G(d, p),对对苯二甲酸乙二醇酯一聚体降解反应机理进行了理论研究.设计了对苯二甲酸乙二醇酯一聚体纯热解、水解和醇解、水或醇作为催化剂降解过程的各种可能反应路径,对参与反应的各种中间体、过渡态及产物进行了几何结构优化和频率计算以获得热力学与动力学参数值.计算结果表明:当水或甲醇作为对苯二甲酸乙二醇酯热降解过程中的催化剂时,利用水或甲醇O-H中H提供到对苯二甲酸乙二醇酯一聚体主链酯键中O原子上形成对苯二甲酸,而乙烷基脱掉的H原子与水中羟基(-OH)或醇中甲氧基(-OCH3)结合形成新的水或者甲醇,从而降低对苯二甲酸乙二醇酯热解过程中的反应能垒(251.4 kJ/mol→181.1 kJ/mol(甲醇)和187.5 kJ/mol(水));当水或甲醇作为对苯二甲酸乙二醇酯热降解过程中的反应物参与反应时,利用水或甲醇O-H中H提供到对苯二甲酸乙二醇酯一聚体主链乙烷基旁O原子上形成乙二醇,而水中羟基(-OH)或醇中甲氧基(-OCH3)结合对苯二甲酸乙二醇酯一聚体主链羰基中C原子上形成对苯二甲酸或对苯二甲酸单... 相似文献
17.
基于密度泛函理论方法研究了HCN气体在Cu(100)、Cu(110)、Cu(111)、Zn(100)、Zn(110)、Zn(111)表面上不同吸附位点的吸附性质,计算并分析了吸附能、电荷转移、电子态密度的特征。研究表明:HCN在Cu不同表面的吸附能分布在-0.42~-0.29 eV区间内,为物理吸附。HCN在Zn不同表面的吸附能相差较大,Zn(111)表面Hollow吸附位点的吸附能为-1.57 eV,为化学吸附。吸附能较大时对应的HCN的键长键角变化率较大。HCN在Zn表面的吸附要强于在Cu表面的吸附。HCN吸附在金属表面后,电子从吸附剂表面转移到HCN上,同一吸附剂表面不同吸附位点的吸附能越大,电子转移数量越多。吸附后HCN态密度曲线整体向低能级移动,峰值降低,其结构变得更加稳定。 相似文献
18.
The reactivity with ethylene of palladium clusters supported on oxidised tungsten foil has been investigated by synchrotron radiation-induced photoelectron spectroscopy and temperature programmed desorption. The effect of the heat pre-treatment of the sample on the interaction strength with ethylene is demonstrated. Already at room temperature, adsorption of ethylene causes breaking of both the C-H and C-C bonds and the appearance of a highly reactive C1 phase with unsaturated bonds. A part of this phase is oxidised to carbon monoxide by oxygen supplied by the support immediately after ethylene adsorption. Another part of ethylene is probably adsorbed in the form of ethylidyne. Heating at temperatures between 400 K and 500 K brings about the dissolution of the C1 phase in the shallow subsurface region of the Pd clusters. Further oxidation of the C1 phase by oxygen from the support proceeds at ∼600 K. Substantial reduction of the concentration of C1 phase at room temperature is observed after heat pre-treatment of the sample at 500 K, while complete suppression of the room temperature ethylene chemisorption proceeds upon heat pre-treatment at 800 K. This effect is related to thermally induced encapsulation of palladium clusters in surface tungsten oxide. 相似文献
19.
Enantioselectivity in gold clusters is investigated by studying the adsorption of a chiral amino acid (cysteine) on a chiral Au55 cluster using density functional calculations. The highest adsorption energies were found when the amino and thiolate functional groups of cysteine are bonded to the lowest coordinated edges of the chiral cluster. Enantiospecific adsorption is primarily obtained from the different bond location and strength, at the cluster edge, of the carboxyl groups forming the left- and right-handed enantiomers. These results provide theoretical support to convey enantioselectivity in asymmetric nanocatalysts using chiral gold clusters. 相似文献
20.
本文利用密度泛函理论研究了Rh原子在(6,6)单壁碳纳米管内外的吸附行为. 通过对Rh在单壁碳纳米管上不同吸附位的吸附构型与吸附能的研究发现: Rh吸附在管内、外的洞位最稳定, 且管外吸附比在管内强. 这是由于单壁碳纳米管的卷曲效应使得管外电荷密度比管内大造成的. 态密度分析表明, 吸附在管内外的Rh原子的5s电子均转移到了4d轨道上; Rh原子4d轨道上的电子转移到了(6, 6)碳管上, 使Rh带正电, 碳管带负电. 结合能带分析表明, Rh原子吸附在管内磁性较弱, 而吸附在管外较强.
关键词:
密度泛函理论
单壁碳纳米管
Rh原子
吸附 相似文献