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1.
ZHANG Cai-rong ZHANG Bi-xia CHEN Yu-hong LI Wei-xue XU Guang-ji 《原子与分子物理学报》2006,23(B04):171-174
The hybrid density functional theory B3LYP with basis sets 6-31G* has been used to study on the equilibrium geometries and electronic structures of possible isomers of Si3N4 clusters. 24 possible isomers are obtained. The most stable isomer of Si3N4 is a 3D structure with 7 Si-N bonds and 2 N-N bonds that could beformed by 3 quadrangles. The bond properties of the most stable isomer was analyzed by using natural bond orbital method (NBO), the results suggest that the charges on Si and N atoms in Si-N bonds are quite large, so theinteraction of N-Si atoms in Si3N4 cluster is of strongly electric interaction. The primary IR and Raman vibrational frequency located at 1033.40 cm^-1, 473.63 cm^-1 respectively. The polarizabilities and hyperpolarizabilities of the most stable isomer are also analyzed. 相似文献
2.
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
3.
Geometric, electronic and vibrational properties of the most stable and energetically favourable configurations of indium oxide clusters InmOn (1≤m, n≤4) are investigated using density functional theory. The lowest energy geometries prefer the planar arrangement of the constituent atoms with a trend to maximize the number of ionic In-O bonds. Due to the charge transfer from In to O atoms, the electrostatic repulsion occurs between the atoms with the same kind of charge. The minimization of electrostatic repulsion and the maximization of In-O bond number compete between each other and determine the location of the isometric total energy. The most stable linear In-O-In-O structure of In2O2 cluster is attributed to the reduced electrostatic repulsive energy at the expense of In-O bond number, while the lowest energy rhombus-like structure of In2O3 cluster reflects the maximized number of In-O bonds. Furthermore, the vibrational frequencies of the lowest energy clusters are calculated and compared with the available experimental results. The energy gap and the charge density distribution for clusters with varying oxygen/indium ratio are also discussed. 相似文献
4.
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. 相似文献
5.
This paper obtains the lowest-energy geometric structures and the
electronic and magnetic properties of small CuNiN clusters by
using all-electron density functional theory. The calculated results
reveal that the Cu atom prefers to occupy the apical site when N
≤ 9 and for the clusters with N=10, the Cu atom starts to
encapsulate in the cage. The CuNi7} and CuNi9 are magic
clusters. The magnetism correlates closely with the symmetry of the
clusters. For these clusters, the charge tends to transfer from the
nickel atoms to the copper atoms. It finds that the doping of Cu
atom decreases the stability of pure NiN clusters. 相似文献
6.
The static dipole polarizabilities of scandium clusters with up to
15 atoms are determined by using the numerically finite field method
in the framework of density functional theory. The electronic
effects on the polarizabilities are investigated for the scandium
clusters. We examine a large highest occupied molecular orbital --- the lowest
occupied molecular orbital (HOMO--LUMO) gap of a scandium cluster
usually corresponds to a large dipole moment. The static
polarizability per atom decreases slowly and exhibits local minimum
with increasing cluster size. The polarizability anisotropy and the
ratio of mean static polarizability to the HOMO--LUMO gap can also
reflect the cluster stability. The polarizability of the scandium
cluster is partially related to the HOMO--LUMO gap and is also
dependent on geometrical characteristics. A strong correlation
between the polarizability and ionization energy is observed. 相似文献
7.
Structural,electronic, and magnetic properties of boron cluster anions doped with aluminum:BnAl-(2〈n〈9) 下载免费PDF全文
The geometrical structures, relative stabilities, electronic and magnetic properties of small BnAl-(2〈n〈9)clusters are systematicalyy investigated by using the first-principles density functional theory. The results show that the A1 atom prefers to reside either on the outer-side or above the surface, but not in the centre of the clusters in all of the most stable BnAl-(2〈n〈9) isomers and the one excess electron is strong enough to modify the geometries of some specific sizes of the neutral clusters. All the results of the analysis for the fragmentation energies, the second-order difference of energies, and the highest occupied-lowest unoccupied molecular orbital energy gaps show that B4A1- and B8A1- clusters each have a higher relative stability. Especially, the BsA1-cluster has the most enhanced chemical stability. Furthermore, both the local magnetic moments and the total magnetic moments display a pronounced oddeven oscillation with the number of boron atoms, and the magnetic effects arise mainly from the boron atoms except for the B7A1- and BgA1- clusters. 相似文献
8.
At the Douglas–Kroll–Hess(DKH) level, the B3PW91 functional along with the all-electron relativistic basis sets of valence triple and quadruple zeta qualities are used to determine the structure, stability, and electronic properties of the small silver clusters(Agn, n≤7). The results presented in this study are in good agreement with the experimental data and theoretical values obtained at a higher level of theory from the literature. Static polarizability and hyperpolarizability are also reported. It is verified that the mean dipole polarizability per atom exhibits an odd-even oscillation and that the polarizability anisotropy is directly related to the cluster shape. In this article, the first study of hyperpolarizabilities of small silver clusters is presented. Except for the monomer, the second hyperpolarizabilities of the silver clusters are significantly larger than those of the copper clusters. 相似文献
9.
Based on the density-functional theory, this paper studies the geometric and magnetic properties of TinO (n=1-9) clusters. The resulting geometries show that the oxygen atom remains on the surface of clusters and does not change the geometry of Tin significantly. The binding energy, second-order energy differences with the size of clusters show that Ti7O cluster is endowed with special stability. The stability of TinO clusters is validated by the recent time-of-flight mass spectra. The total magnetic moments for TinO clusters with n=1-4, 8-9 are constant with 2 and drop to zero at n=5-7. The local magnetic moment and charge partition of each atom, and the density of states are discussed. The magnetic moment of the TinO is clearly dominated by the localized 3d electrons of Ti atoms while the oxygen atom contributes a very small amount of spin in TinO clusters. 相似文献
10.
The general features of the geometries and electronic properties for 3d,4d,and 5d transition-metal atom doped Au 6 clusters are systematically investigated by using relativistic all-electron density functional theory in the generalized gradient approximation(GGA).A number of structural isomers are considered to search the lowest-energy structures of M@Au 6 clusters(M=3d,4d and 5d transition-metal atoms),and the transition metal atom locating in the centre of an Au 6 ring is found to be in the ground state for all the M@Au 6 clusters.All doped clusters,expect for Pd@Au 6,show large relative binding energies compared with a pure Au 7 cluster,indicating that doping by 3d,4d,5d transition-metal atoms could stabilize the Au 6 ring and promote the formation of a new binary alloy cluster. 相似文献
11.
Equilibrium geometries and electronic properties of BenLi (n=2-15) clusters from first principles 下载免费PDF全文
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. 相似文献
12.
This paper reports that the YBa2Cu3-xZnxO7-δ (x = 0-0.4) samples are researched by means of x-ray diffraction, calculations of binding energy, the positron experiments and variations of oxygen content. The results of simulated calculations, positron experiments and variations of oxygen content support the existence of cluster effect. Moreover, it is concluded that the cluster effect is an important factor on suppression of high-Tc cuprate superconductivity and the Tc does not depend on the density of valence electron directly. 相似文献
13.
First-principles study of structures and electronic properties of cadmium sulfide clusters 下载免费PDF全文
The lowest-energy structures and the electronic properties of CdnSn (n = 1 - 8) clusters have been studied by using denslty-functional theory simulating package DMol^3 in the generalized gradient approximation (GGA). The ring-like structures are the lowest-energy configurations for n = 2, 3 and the three-dimensional spheroid configurations for n = 4 - 8. The three-dimensional structures may be considered as being built from the Cd2S2 and Cd3S3 rings. Compared to the previous reports, we have found the more stable structures for CdnSn(n = 7, 8). Calculations show that the magic numbers of CdnSn (n = 1-8) clusters are n = 3 and 6. As cluster size increases, the properties of CdnSn clusters tend to bulk-like ones in binding energy per CdS unit and Mulliken atomic charge, obtained by comparing with the calculated results of the wurtzite and zinc blende CdS for the same simulating parameters. 相似文献
14.
First-principles investigation of BAs and BxGa1-xAs alloys Using first-principles calculations in the generalized gradient approximation, the electronic properties of BAs and BxGa1-xAs alloys are studied. At the Brillouin-zone centre, the lowest conduction band is the three-degenerate p-like Г15c state rather than s-like Г1c state, and the conduction band minimum (CBM) is along the A line between the Г and X points-at approximately 11/14(1,0,0)2π/a. With boron content at 0%-18.75%, BxGa1-xAs alloys have a small (2.6 eV) and relatively composition-independent band-gap bowing parameter, the band-gap increases monotonically by -18meV/B% with increasing boron content. In addition, the formation enthalpies of mixing for BxGa1-xAs alloys with boron content at 6.25% and 12.5% are calculated, and the large formation enthalpies may explain the difficulty in alloying boron to GaAs. 相似文献
15.
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. 相似文献
16.
First-principles study of interphase Ni3Sn in Sn--Ni alloy for anode of lithium ion battery 下载免费PDF全文
This paper investigates the mechanism of Li insertion into interphase Ni3Sn in Ni-Sn alloy for the anode of lithium ion battery by means of the first-principles plane-wave pseudopotential. Compared with other phases, it is found that the Ni3Sn has larger relative expansion ratio and lower electrochemical potential, with its specific plateaus voltage around 0.3 eV when lithium atoms are filled in all octahedral interstitial sites, and the relative expansion ratio increasing dramatically when the lithiated phase transits from octahedral interstitial sites to tetrahedral interstitial sites. So this phase is a devastating phase for whole alloy electrode materials. 相似文献
17.
The hole subband structures and effective masses of tensile strained Si/Sil-yGey quantum wells are calculated by using the 6 × 6 k·p method. The results show that when the tensile strain is induced in the quantum well, the light-hole state becomes the ground state, and the light hole effective masses in the growth direction are strongly reduced while the in-plane effective masses are considerable. Quantitative calculation of the valence intersubband transition between two light hole states in a 7nm tensile strained Si/Si0.55Ge0.45 quantum well grown on a relaxed Si0.5Ge0.5 (100) substrates shows a large absorption coefficient of 8400 cm^-1. 相似文献
18.
This paper studies the coalescence of heteroclusters Au767 and Ag767 by using molecular dynamics with the embedded atom method, where layer atomic energy is employed to describe the potential energy variation of per atom in different layers along radial direction. The results show that the coalescence is driven by releasing the atomic energy of the coalesced zone. The deformation, which is induced by substitutional and vacancy diffusion during the coalescence, makes the coalesced cluster disorder. If the summation of the thermal energy and the released atomic energy is large enough to keep the disorder state, the clusters form a metastable liquid droplet; otherwise, the clusters coalesce into a solid cluster when the coalesced cluster reaches the equilibrium state, and the coalesced cluster experiences liquid to solid ordering changes during the coalescence of a solid Au767 with a liquid Ag767 and a liquid Au767 with a liquid Ag767. The centre of figure of the cluster system is shifted during the coalescence process, and higher coalescence temperature causes larger shift degree. 相似文献
19.
Compact efficient optical parametric generator internal to a Q-switched Nd:YVO4 laser with periodically poled MgO:LiNbO3 下载免费PDF全文
This paper demonstrates a compact efficient optical parametric
generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching,
intracavity optical parametric generator, periodically poled
MgO-doped lithium niobate (PPMgLN) Project supported by the National
Natural Science Foundation of China (Grant Nos 10474071 and
60671036). 4265K, 4260F, 4270 This paper demonstrates a compact efficient optical parametric
generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching,
intracavity optical parametric generator, periodically poled
MgO-doped lithium niobate (PPMgLN) Project supported by the National
Natural Science Foundation of China (Grant Nos 10474071 and
60671036). 4265K, 4260F, 4270 This paper demonstrates a compact efficient optical parametric
generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching,
intracavity optical parametric generator, periodically poled
MgO-doped lithium niobate (PPMgLN) Project supported by the National
Natural Science Foundation of China (Grant Nos 10474071 and
60671036). 4265K, 4260F, 4270 This paper demonstrates a compact efficient optical parametric
generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching,
intracavity optical parametric generator, periodically poled
MgO-doped lithium niobate (PPMgLN) Project supported by the National
Natural Science Foundation of China (Grant Nos 10474071 and
60671036). 4265K, 4260F, 4270 This paper demonstrates a compact efficient optical parametric
generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching,
intracavity optical parametric generator, periodically poled
MgO-doped lithium niobate (PPMgLN) Project supported by the National
Natural Science Foundation of China (Grant Nos 10474071 and
60671036). 4265K, 4260F, 4270 This paper demonstrates a compact efficient optical parametric
generator internal to a Q-switched diode-end-pumped Nd:YVO$_{4}$
laser with periodically poled MgO:LiNbO3(PPMgLN). With the
Q-switch set at a repetition rate of 25kHz and the PPMgLN crystal
operated at room temperature (25\du\,), the intracavity optical
parametric generator threshold was reached as a diode pump power of
0.9\,W. A maximum signal output power of 0.34W with a pulse width
of 25\,ns and a beam quality factor of 1.4 was obtained at an
incident diode power of 3.4\,W, leading to a conversion efficiency of
10{\%} with a slope efficiency of 14.4{\%}. By varying the crystal
temperature from 25 to 200\du, the output signal wavelengths were
tuned in range of 1506--1565\,nm. Over a 30-minutes interval, the
instability of the signal power was measured to be less than 1{\%}.
In addition, the threshold pump intensity for the intracavity optical
parametric generator is theoretically investigated, and the obtained
result is in good agreement with the experimental results. 相似文献
20.
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