共查询到20条相似文献,搜索用时 500 毫秒
1.
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
2.
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
3.
A systematic study on the structure and electronic properties of gold clusters doped each with one copper atom has been performed using the density functional theory. The average bond lengths in the Aun-1Cu (n ≤ 9) bimetallic clusters are shorter than those in the corresponding pure gold clusters. The ionization potentials of the bimetallic clusters Aun-1Cu (n 〈 9) are larger than those of the corresponding homoatomic gold clusters except for Aus. The energy gaps of the Au-Cu binary clusters are narrower than those of the Aun clusters except AuCu and Au3Cu. No obvious even-odd effect exists in the variations of the electron affinities and ionization potentials for the Aun-1Cu (n ≤ 9) clusters, which is in contrast to the case of gold clusters Aun. 相似文献
4.
Anomalous Hall effect of facing-target sputtered ferrimagnetic Mn4N epitaxial films with perpendicular magnetic anisotropy
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zeyu Zhang 《中国物理 B》2022,31(4):47305-047305
Epitaxial Mn$_{4}$N films with different thicknesses were fabricated by facing-target reactive sputtering and their anomalous Hall effect (AHE) is investigated systematically. The Hall resistivity shows a reversed magnetic hysteresis loop with the magnetic field. The magnitude of the anomalous Hall resistivity sharply decreases with decreasing temperature from 300 K to 150 K. The AHE scaling law in Mn$_{4}$N films is influenced by the temperature-dependent magnetization, carrier concentration and interfacial scattering. Different scaling laws are used to distinguish the various contributions of AHE mechanisms. The scaling exponent $\gamma > 2$ for the conventional scaling in Mn$_{4}$N films could be attributed to the residual resistivity $\rho_{xx0}$. The longitudinal conductivity $\sigma_{xx}$ falls into the dirty regime. The scaling of $\rho_{\rm AH}=\alpha \rho_{xx0} +b\rho_{xx}^{n}$ is used to separate out the temperature-independent $\rho_{xx0}$ from extrinsic contribution. Moreover, the relationship between $\rho_{\rm AH}$ and $\rho_{xx}$ is fitted by the proper scaling to clarify the contributions from extrinsic and intrinsic mechanisms of AHE, which demonstrates that the dominant mechanism of AHE in the Mn$_{4}$N films can be ascribed to the competition between skew scattering, side jump and the intrinsic mechanisms. 相似文献
5.
A polarization mismatched p-GaN/p-Al0.25Ga0.75N/p-GaN structure to improve the hole injection for GaN based micro-LED with secondary etched mesa
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yidan Zhang 《中国物理 B》2023,32(1):18509-018509
A low hole injection efficiency for InGaN/GaN micro-light-emitting diodes (μLEDs) has become one of the main bottlenecks affecting the improvement of the external quantum efficiency (EQE) and the optical power. In this work, we propose and fabricate a polarization mismatched p-GaN/p-Al$_{0.25}$Ga$_{0.75}$N/p-GaN structure for 445 nm GaN-based μLEDs with the size of $40 \times 40 $μm$^{2}$, which serves as the hole injection layer. The polarization-induced electric field in the p-GaN/p-Al$_{0.25}$Ga$_{0.75}$N/p-GaN structure provides holes with more energy and can facilitate the non-equilibrium holes to transport into the active region for radiative recombination. Meanwhile, a secondary etched mesa for μLEDs is also designed, which can effectively keep the holes apart from the defected region of the mesa sidewalls, and the surface nonradiative recombination can be suppressed. Therefore, the proposed μLED with the secondary etched mesa and the p-GaN/p-Al$_{0.25}$Ga$_{0.75}$N/p-GaN structure has the enhanced EQE and the improved optical power density when compared with the μLED without such designs. 相似文献
6.
The low-energy structures and the electronic and the
magnetic properties of small NiNiNi$_{m}$Ti$_{n}$ clusters, lowest-energy structure,
electronic and magnetic properties Project supported by the National
Natural Science Foundation of China (Grant No.~10874039), and the
Natural Science Foundation of Hebei Province of China (Grant
Nos.~A2009000246 and 2009000243). 3120A, 3640B, 2110K 7/3/2009 12:00:00 AM The low-energy structures and the electronic and the
magnetic properties of small NiNiNi$_{m}$Ti$_{n}$ clusters, lowest-energy structure,
electronic and magnetic properties Project supported by the National
Natural Science Foundation of China (Grant No.~10874039), and the
Natural Science Foundation of Hebei Province of China (Grant
Nos.~A2009000246 and 2009000243). 3120A, 3640B, 2110K 7/3/2009 12:00:00 AM The low-energy structures and the electronic and the
magnetic properties of small Ni$_{n}$Ti$_{n}$ ($n=1$--$6$) and
Ni$_{m}$Ti$_{n}$ ($1 \le n \le 4$, $1 \le m \le 4$, $n \ne m$)
clusters are investigated by performing all-electron calculations
based on density functional theory. Ground states and several
isomers near the ground states are determined for these clusters.
The results indicate that the growth of small Ni$_{m}$Ti$_{n}$
clusters prefers to form rich Ti--Ni and Ti--Ti bonds. When the
percentage of titanium atoms is significantly greater than that of
nickel atoms, the nickel atoms are most frequently found above
the surface; in contrast, the titanium atoms prefer the bridging
sites. A M\"{u}lliken spin population analysis indicates that the
total spin of titanium-nickel clusters is not always zero. http://cpb.iphy.ac.cn/CN/10.1088/1674-1056/19/4/043102 https://cpb.iphy.ac.cn/CN/article/downloadArticleFile.do?attachType=PDF&id=111644 NimTin;clusters;lowest-energy;structure;electronic;and;magnetic;properties The low-energy structures and the electronic and the magnetic properties of small Nin Tin(n = 1-6) and Ni m Ti n(1 ≤ n ≤ 4,1 ≤ m ≤ 4,n ≠ m) clusters are investigated by performing all-electron calculations based on density functional theory.Ground states and several isomers near the ground states are determined for these clusters.The results indicate that the growth of small Ni m Ti n clusters prefers to form rich Ti-Ni and Ti-Ti bonds.When the percentage of titanium atoms is significantly greater than that of nickel atoms,the nickel atoms are most frequently found above the surface;in contrast,the titanium atoms prefer the bridging sites.A Mu¨lliken spin population analysis indicates that the total spin of titanium-nickel clusters is not always zero. 相似文献
7.
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
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
8.
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
9.
Scattering behaviours to the two-dimensional electron gasinduced by the Al composition fluctuation in AlxGa1-xNbarrier in AlxGa1-xN/GaN heterostructures
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
<正>This paper reports that cathodoluminescence(CL) measurements have been done to study the alloy fluctuation of the Al0.3Ga0.7N layer in Al0.3Ga0.7N/GaN heterostructures.The CL images and linescanning results demonstrate the existence of compositional fluctuation of Al in the Al0.3Ga0.7N barrier.A model using aδ-shape perturbation Hamilton function has been proposed to simulate the scattering probability of the two dimensional electron gases (2DEG) induced by Al composition fluctuation.Two factors,including conduction band fluctuation and polarization electric field variation,induced by the Al composition fluctuation have been taken into account.The scattering relaxation time induced by both factors has been estimated to be 0.31 ns and 0.0078 ns,respectively,indicating that the variation of the piezoelectric field is dominant in the scattering of the 2DEG induced by Al fluctuation. 相似文献
10.
Equilibrium geometries and electronic properties of BenLi (n=2-15) clusters from first principles
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
11.
利用可加性规则,使用Hartree-Fock波函数,采用由束缚原子概念修正过的复光学势,在30~5000eV这一较大的能域内对电子被N2、NO、NO2、CH4、CF4、CF3H、C2H2及C2H4散射的总截面进行了计算。束缚原子不同于自由原子之处,是束缚原子概念考虑了不同分子中的不同的电子云重叠情况,并根据电子云的重叠情况对复光学势进行修正。文中,将定量的计算结果与实验结果及其它理论计算结果进行了比较,结果显示出在30~5000eV内,计算结果与实验结果及其它理论计算结果间有较好的一致性。同时结果也表明,在较低的能量下,尤其是当入射电子的能量低于500eV时,利用被束缚原子概念修正过的复光学势进行计算得到的结果,要比利用未被束缚原子概念修正的复光学势计算得到的结果更接近于实验值。因此,在复光学势中考虑电子云的重叠效应可改善电子被分子散射的总截面的计算精度。 相似文献
12.
Alloying and magnetic disordering effects on phase stability of Co2 YGa (Y=Cr,V, and Ni) alloys: A first-principles study
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chun-Mei Li 《中国物理 B》2022,31(5):56105-056105
The alloying and magnetic disordering effects on site occupation, elastic property, and phase stability of Co$_{2}Y$Ga ($Y={\rm Cr}$, V, and Ni) shape memory alloys are systematically investigated using the first-principles exact muffin-tin orbitals method. It is shown that with the increasing magnetic disordering degree $y$, their tetragonal shear elastic constant $C'$ (i.e., $(C_{11}-C_{12})/2$) of the $L2_{1}$ phase decreases whereas the elastic anisotropy $A$ increases, and upon tetragonal distortions the cubic phase gets more and more unstable. Co$_{2}$CrGa and Co$_{2}$VGa alloys with $y\geq0.2$ thus can show the martensitic transformation (MT) from $L2_{1}$ to $D0_{22}$ as well as Co$_{2}$NiGa. In off-stoichiometric alloys, the site preference is controlled by both the alloying and magnetic effects. At the ferromagnetism state, the excessive Ga atoms always tend to take the $Y$ sublattices, whereas the excessive Co atom favor the $Y$ sites when $Y={\rm Cr}$, and the excessive $Y$ atoms prefer the Co sites when $Y={\rm Ni}$. The Ga-deficient $Y={\rm V}$ alloys can also occur the MT at the ferromagnetism state by means of Co or V doping, and the MT temperature $T_{\rm M}$ should increase with their addition. In the corresponding ferromagnetism $Y={\rm Cr}$ alloys, nevertheless, with Co or Cr substituting for Ga, the reentrant MT (RMT) from $D0_{22}$ to $L2_{1}$ is promoted and then $T_{\rm M}$ for the RMT should decrease. The alloying effect on the MT of these alloys is finally well explained by means of the Jahn-Teller effect at the paramagnetic state. At the ferromagnetism state, it may originate from the competition between the austenite and martensite about their strength of the covalent banding between Co and Ga as well as $Y$ and Ga. 相似文献
13.
Co-Al-W基高温合金具有类似于Ni基高温合金的γ+γ'相组织结构.根据面心立方固溶体的团簇加连接原子结构模型,Ni基高温合金的成分式即最稳定的化学近程序结构单元可以描述为第一近邻配位多面体团簇加上次近邻的三个连接原子.本文应用类似方法,首次给出了Co-Al-W基高温合金的团簇成分式.利用原子半径和团簇共振模型,可计算出Co-Al-W三元合金的团簇成分通式,为[Al-Co_(12)](Co,Al,W)_3,即以Al为中心原子、Co为壳层原子的[Al-Co_(12)]团簇加上三个连接原子.对于多元合金,需要先将元素进行分类:溶剂元素——类Co元素Co (Co, Cr, Fe, Re, Ni,Ir,Ru)和溶质元素——类Al元素Al (Al,W,Mo, Ta,Ti,Nb,V等);进而根据合金元素的配分行为,将类Co元素分为Co~γ(Cr, Fe, Re)和Co~(γ')(Ni, Ir, Ru);根据混合焓,将类Al元素分为Al, W (W, Mo)和Ta (Ta, Ti, Nb, V等).由此,任何多元Co-Al-W基高温合金均可简化为Co-Al伪二元体系或者Co-Al-(W,Ta)伪三元体系,其团簇加连接原子成分式为[Al-Co_(12)](Co_(1.0)Al_(2.0))(或[Al-Co_(12)] Co_(1.0)Al_(0.5)(W,Ta)_(1.5)=Co_(81.250)Al_(9.375)(W,Ta)_(9.375) at.%).其中,γ与γ'相的团簇成分式分别为[Al-Co_(12)](Co_(1.5)Al_(1.5))(或[Al-Co_(12)] Co_(1.5)Al_(0.5)(W,Ta)_(1.0)=Co_(84.375)Al_(9.375)(W,Ta)_(6.250) at.%)和[Al-Co_(12)](Co_(0.5)Al_(2.5))(或[Al-Co_(12)] Co_(0.5)Al_(0.5)(W, Ta)_(2.0)=Co_(78.125)Al_(9.375)(W,Ta)_(12.500)at.%).例如,Co_(82)Al_9W_9合金的团簇成分式为[Al-Co_(12)]Co_(1.1)Al_(0.4)W_(1.4)(~[Al-Co_(12)]Co_(1.0)Al_(0.5)W_(1.5)),其中γ相的团簇成分式为[Al-Co_(12)]Co_(1.6)Al_(0.4)W_(1.0)(~[Al-Co_(12)]Co_(1.5)Al_(0.5)W_(1.0)),γ'相的团簇成分式为[Al-Co_(12)]Co_(0.3)Al_(0.5)W_(2.2)(~[AlCo_(12)]Co_(0.5)Al_(0.5)W_(2.0)). 相似文献
14.
In order to understand the recycling and emission processes of hydrogen atoms in HT 7, spectral profiles of the Dα(Hα) line emitted in front of the limiter have been observed with a high-resolution spectrometer and simulated by using the neutral particle transport code DEGAS 2. The results show that four processes are necessary to interpret the Dα(Hα) line shape: 1) atom desorption, 2) molecular dissociation, 3) particle reflection, and 4) charge-exchange. The products of the first two processes are cold atoms which emit photons near the peak of Dα(Hα) line shape, and those from the last two are warm atoms contributing to the blue side of the spectrum. For a typical ohmic discharge (shot 68520 ne(0) ≈ 3× 10^19 m^-3. these components contribute 32%, 15%, 32% and 21%, respectively. Dα(Hα) line shapes under different plasma parameters are also discussed in this paper. 相似文献
15.
The structures and properties of Wn (n=2--14) clusters were
studied by using the density functional theory (DFT) at LSDA level. The
most stable structures of Wn (n=2--14) clusters with global
minimum were determined. The average binding energy (Eb), the
first and second difference of total energy (\itδ E,
\itδ2E), the vertical detachment energy (VDE), and the
HOMO-LUMO gap versus the size were also discussed. The abrupt
decrease of VDE and HOMO-LUMO gap at size n=8 and 10 implied
that tungsten clusters of W8 and W10 appeared to have
metallic features. These changes were also accompanied by the
delocalization of electron charge density and the strong
hybridization between 5d and 6s orbits in W8 and W_10
clusters. Our results are in good agreement with the available
experimental data. 相似文献
16.
Resonances of a hydrogen atom in strong parallel electric and magnetic fields using B-spline basis sets
下载免费PDF全文
![点击此处可从《物理学报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The B-spline basis set plus complex scaling method is applied to the
numerical calculation of the exact resonance parameters $E_r}$
and $\Ga/2$ of a hydrogen atom in parallel electric and magnetic
fields. The method can calculate the ground and higher excited
resonances accurately and efficiently. The resonance parameters with
accuracies of $10^{-9}-10^{-12}$ for hydrogen atom in parallel
fields with different field strengths and symmetries are presented
and compared with previous ones. Extension to the calculation of
Rydberg atom in crossed electric and magnetic fields and of atomic
double excited states in external electric fields is discussed. 相似文献
17.
Resonances of a hydrogen atom in strong parallel electric and magnetic fields using B-spline basis sets
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The B-spline basis set plus complex scaling method is applied to the numerical calculation of the exact resonance parameters Er and Г/2 of a hydrogen atom in parallel electric and magnetic fields. The method can calculate the ground and higher excited resonances accurately and efficiently. The resonance parameters with accuracies of 10^-9 - 10^-12 for hydrogen atom in parallel fields with different field strengths and symmetries are presented and compared with previous ones. Extension to the calculation of Rydberg atom in crossed electric and magnetic fields and of atomic double excited states in external electric fields is discussed. 相似文献
18.
Impact of AlxGa1-xN barrier thickness and Al composition on electrical properties of ferroelectric HfZrO/Al2O3/AlGaN/GaN MFSHEMTs
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ferroelectric (FE) HfZrO/Al$_{2}$O$_{3}$ gate stack AlGaN/GaN metal-FE-semiconductor heterostructure high-electron mobility transistors (MFSHEMTs) with varying Al$_{x}$Ga$_{1-x}$N barrier thickness and Al composition are investigated and compared by TCAD simulation with non-FE HfO$_{2}$/Al$_{2}$O$_{3}$ gate stack metal-insulator-semiconductor heterostructure high-electron mobility transistors (MISHEMTs). Results show that the decrease of the two-dimensional electron gas (2DEG) density with decreasing AlGaN barrier thickness is more effectively suppressed in MFSHEMTs than that in MISHEMTs due to the enhanced FE polarization switching efficiency. The electrical characteristics of MFSHEMTs, including transconductance, subthreshold swing, and on-state current, effectively improve with decreasing AlGaN thickness in MFSHEMTs. High Al composition in AlGaN barrier layers that are under 3-nm thickness plays a great role in enhancing the 2DEG density and FE polarization in MFSHEMTs, improving the transconductance and the on-state current. The subthreshold swing and threshold voltage can be reduced by decreasing the AlGaN thickness and Al composition in MFSHEMTs, affording favorable conditions for further enhancing the device. 相似文献
19.
The first-principles study of ferroelectric behaviours of PbTiO3/SrTiO3 and BaTiOn/SrTiO3 superlattices
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We have performed the first-principles calculation to investigate the origins of ferroelectricities and different po- larization behaviours of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. The density of state (DOS) and electronic charge profiles show that there are strong hybridizations between atoms Ti and O and between atoms Pb and O which play very important roles in producing the ferroelectricities of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. Ow- ing to the decline of internal electric field in SrTiO3 (ST) layer, the tetragonality and polarizations of superlattices decrease with increasing the fraction of SrTiO3 in the superlattices. We find that the polarization of PbTiO3/SrTiO3 is largerthan that of BaTiO3/SrTiO3 at the same ratio of components, because the polarization mismatch between PbTiO3 and SrTiO3 is larger than that between BaTiO3 and SrTiO3. The polarization and tetragonality are en- hanced with respect to those of bulk tetragonal BaTiO3 in the superlattices BaTiO3/SrTiO3, while the polarization and tetragonality are reduced with respect to those of bulk tetragonal PbTiO3 in superlattices PbTiO3/SrTiO3. 相似文献
20.
J. G. Du X. Y. Sun G. Jiang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(1):111-120
The equilibrium structures, electronic properties of bimetallic Ti1-4M
(M=V, Fe, Ni) clusters are investigated by using the density functional
method within generalized gradient approximation in conjunction with the
valence basis set. Considering the spin multiplicity effect, the geometries
with different spins are optimized to find the ground states. For the ground
states, the natural bonding orbital analysis (NBO) is performed and shows
that the 4s electrons always transfer to the 3d orbital in the bonding atoms
so that 4s and 3d orbitals hybridize with each other. The electron transfers
from Ti atoms to the ‘impurity’ atoms (V, Fe, and Ni) are also found. The
two kinds of electron transfer mechanisms are considered to be the
contributor for the stabilities of the studied clusters. The Wiberg bond order and
AIM (atoms in molecules) analyses indicate that the relative stabilities of
chemical bonds are: $\text{Ti-V/Ti-Fe} > \text{Ti-Ti} > \text{Ti-Ni}$\text{Ti-V/Ti-Fe} > \text{Ti-Ti} > \text{Ti-Ni}. The spin magnetic
moments are found to be mostly located at Ti atoms. Several clusters like
Ti2V, Ti3V, Ti3Ni and Ti4Ni present the high moments. 相似文献