共查询到20条相似文献,搜索用时 156 毫秒
1.
利用第一性原理计算方法,研究了CuHg2Ti结构下Ti2CrK(K=Sb,Ge,Sn,Sb,Bi)系列合金的电子结构、能隙起源和磁性.研究发现:Ti2CrK(K=Si,Ge)合金是普通半导体材料;Ti2CrK(K=Si,Bi)合金是亚铁磁性半金属材料,其半金属性能隙受到Sb和Bi原子s态的直接影响;Ti2CrSn合金是完全补偿的亚铁磁性半导体.基于Ti2CrSn合金两个自旋方向上的能隙起源不同,通过Si和Ge替换掺杂同族Sn元素调制能隙的宽度,获得了完全补偿亚铁磁性自旋无能隙材料;通过Fe和Mn替换掺杂过渡族Cr元素获得了一系列半金属材料.Ti2Cr1-xFexSn和Ti2Cr1-xMnxSn合金都具有亚铁磁性.所研究的这些半金属性合金的分子磁矩Mtotal与总的价电子数Zt服从Mtotal=Zt-18规则. 相似文献
2.
《物理学报》2017,(5)
采用第一性原理的密度泛函理论平面波赝势法,通过广义梯度近似研究了Ti_3AC_2相(A=Si,Sn,Al,Ge)的相结构、能量、电子结构和弹性性质.首先对六方晶相结构的Ti_3AC_2(A=Si,Sn,Al,Ge)四个相进行几何优化,对其能带结构、总态密度、分态密度和电荷密度分布以及弹性性质进行研究,并计算各相的内聚能与形成能.计算结果表明:Ti_3GeC_2较其他三相稳定,Ti_3AlC_2的形成能最低,说明Ti_3AlC_2较Ti_3SiC_2,Ti_3SnC_2和Ti_3GeC_2更易生成;Ti_3AC_2(A=Si,Sn,Al,Ge)各相在费米能级处的电子态密度较高,材料表现出较强的金属性,同时各相的导电性为各向异性.Ti_3AC_2(A=Si,Sn,Al,Ge)各相的导电性主要由Ti的3d电子决定,A(A=Si,Sn,Al,Ge)的p态电子和C的2p态电子也有少量贡献.决定材料电学性质的主要是Ti的3d,A的P和C的2P态电子的P-d电子轨道杂化,而P-d电子轨道杂化成键则使材料具有比较稳定的结构;对Ti_3AC_2相(A=Si,Sn,Al,Ge)弹性性质的研究表明Ti_3AlC_2的原子间结合力较弱,而Ti_3GeC_2的原子间结合力相对较强,材料的强度较大. 相似文献
3.
4.
通过第一原理计算理论预测了CoMnZnZ (Z=Si, Ge, Sn, Pb)系列Heusler合金的弹性常数、电子结构和磁性,并根据弹性常数计算得到弹性模量等参量,计算了该系列化合物声速和德拜温度.计算采用全势线性缀加平面波方法,交换相关函数采用基于Perdew-Burke-Ernzerhof的广义梯度近似泛函.弹性模量结果表明晶体呈现韧性特征;承受剪切的性能弱于承受单轴压缩的性能;结构组成具有较低的各向异性性能.电子结构的计算显示CoMnZnZ (Z=Si, Ge, Sn)三个化合物属于半金属铁磁体,但是CoMnZnPb化合物并不显示半金属特性. CoMnZnZ (Z=Si, Ge, Sn)三个化合物的磁矩通过Slater-Pauling法则进行计算得到的量值与第一原理计算得到的完全一致,遵从总的价电子数减去28的Slater-Pauling法则,三个化合物磁矩为整数且自旋极化率为100%.利用轨道杂化理论解释了此系列化合物半金属性的根源. 相似文献
5.
6.
7.
8.
9.
Na_2Ge_2Se_5是一种优异的红外非线性晶体材料.采用基于第一性原理的密度泛函理论赝势平面波方法对Na_2Ge_2Se_5进行结构优化,并以此为基础计算研究了Na_2Ge_2Se_5的电子结构和光学性质.结果表明:Na2Ge2Se5是宽禁带间接带隙半导体,价带至导带的电子跃迁主要来自于Ge和Se的48,4p态;Na对光学性质的贡献较小,Ge和Se之间的相互耦合作用决定了Na_2Ge_2Se_5的光学性质;该晶体在紫外区有强烈的反射和吸收,静态折射率为2.133,双折射率值适中,为0.145.理论计算结果表明,Na_2Ge_2Se_5是一种性能优良的红外非线性光学晶体材料. 相似文献
10.
利用第一性原理模拟计算了Ga掺杂Ge及Ga、O共掺杂Ge材料的电子结构,对态密度、能带结构进行了分析。结果表明,Ga掺杂Ge材料会使掺杂体系表现为较强的金属性;Ga、O共掺杂会使掺杂体系在低能端出现新的禁带区域。通过掺杂能够改变Ge材料的电学和光学特性。 相似文献
11.
X. G. Kong Y. Yu T. Gao 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,76(3):365-371
The ab initio pseudopotential method within the
generalized gradient approximation (GGA) and quasiparticle approximation has
been used to investigate the electronic properties of titanium dioxide in
the rutile, anatase, and fluorite structures, respectively. Here we present
the GW approximation for the electronic self-energy, which allows to
calculate excited-state properties, especially electronic band structures.
For this calculation, good agreement with the experimental results for the
minimum band gaps in rutile and anatase phase is obtained. In the fluorite
phase we predict that titanium dioxide will be an indirect (Γ to X)
wide band-gap semiconductor (2.367 or 2.369 eV) and the properties remain to
be confirmed by experiment. 相似文献
12.
A photonic band structure of colloidal crystals of silica spheres is analytically determined by a band model with three fitting parameters: the sphere size, the effective refractive index, and the band-gap. Optical properties of the crystals annealed at various temperatures were characterized by a procedure similar to X-ray diffraction technique, and the width of photonic band-gap measured from the transmission spectra experimentally servers as an additional check on the validation of the model. The photonic band structures defined by the band-gap, the refractive index, and the Brillouin zone are obviously superior to the use of the Bragg's expression involving simple zone folding. 相似文献
13.
三维声子晶体带结构研究 总被引:1,自引:0,他引:1
运用平面波展开法计算由长方体散射物以面心立方结构排列于基体中形成的三维声子晶体的带结构,研究不同组分材料、散射物的填充率和长方体散射物的高与长之比 R_(HL)对带隙的影响.结果表明,将质量密度和波速大的散射体放在质量密度和波速小的基体中所形成的三维(面心立方)固态声子晶体有利于带隙的产生;散射体的填充率为中间值时带隙最宽;散射体的对称性强烈影响带隙,当 R_(HL)大于等于1时,带隙宽度随 R_(HL)的增加而减小,相反,当 R_(HL)小于1时,带隙宽度随 R_(HL)的增加而增加. 相似文献
14.
The N-doping effects on the electronic properties of Cu2O crystals are investigated using density functional theory.The calculated results show that N-doped Cu2O with or without oxygen vacancy exhibits different modifications of electronic band structure.In N anion-doped Cu2O,some N 2p states overlap and mix with the O2p valence band,leading to a slight narrowing of band gap compared with the undoped Cu2O.However,it is found that the coexistence of both N impurity and oxygen vacancy contributes to band gap widening which may account for the experimentally observed optical band gap widening by N doping. 相似文献
15.
借助于平面波展开法分析了二维复式格子声子晶体能带结构,计算了铝合金柱体按周期性结构排列在空气中形成的二维固/气复合体系的声子晶体,给出了复式蜂窝格子和复式Kagome格子的能带结构,进而对比分析了复式格子和简单格子的能带结构特性.结果表明,与简单格子相比,复式格子的带隙出现在频率相对较低的位置;在f=0.091—0.6046范围内,将声子晶体排列为复式格子要优于简单格子,可以得到更宽带隙.此外,引入了带隙分布图,讨论了填充系数f对带隙数目、带隙宽度以及带隙上下边界频率的影响.
关键词:
声子晶体
复式格子
带隙
平面波算法 相似文献
16.
V. A. Tolmachev 《Optics and Spectroscopy》2017,122(4):646-660
The theoretical and experimental investigations of photonic band gaps in one-dimensional photonic crystals created by micromatchining silicon, which have been performed by the author as part of his doctoral dissertation, are presented. The most important result of the work is the development of a method of modeling photonic crystals based on photonic band gap maps plotted in structure–property coordinates, which can be used with any optical materials and in any region of electromagnetic radiation, and also for nonperiodic structures. This method made it possible to realize the targeted control of the optical contrast of photonic crystals and to predict the optical properties of optical heterostructures and three-component and composite photonic crystals. The theoretical findings were experimentally implemented using methods of micromatchining silicon, which can be incorporated into modern technological lines for the production of microchips. In the IR spectra of a designed and a fabricated optical heterostructure (a composite photonic crystal), extended bands with high reflectivities were obtained. In a Si-based three-component photonic crystal, broad transmission bands and photonic band gaps in the middle IR region have been predicted and experimentally demonstrated for the first time. Si–liquid crystal periodic structures with electric-field tunable photonic band-gap edges have been investigated. The one-dimensional photonic crystals developed based on micromatchining silicon can serve as a basis for creating components of optical processors, as well as highly sensitive chemical and biological sensors in a wide region of the IR spectrum (from 1 to 20 μm) for lab-on-a-chip applications. 相似文献
17.
The fantastic physical properties of single-walled silicon nanotubes (SWSiNTs) under mechanical strain make them promising
materials for fabricating nanoscale electronic devices or transducers. Here we investigate the energy band and band-gap properties
of the SWSiNTs calculated from the tight-binding model approximation. The results show that the band-gap properties are very
sensitive to the deformation degree and the helicity of the SWSiNTs. The results can be employed to guide the design of nanoelectronic
devices based on silicon nanotubes. 相似文献
18.
We use the changes of colloidal photonic crystal photonic band-gap center wavelength to research the refractive index sensing by experiment. The changes in the center wavelength of the colloidal crystals photonic band-gap are analyzed. A mold is designed to obtain a controllable self-assembly method, colloidal crystals are observed by scan electronic microscope (SEM) and the band-gap is measured by infrared spectrometer. The results are agreed well with the theoretical analysis. An experimental device is designed to test liquid refractive index. The couple of the fibers are used to measure the band-gap of colloidal crystals and the results are also discussed in theory. The results show that the band-gap of colloidal crystals can be used to measure the liquid refractive index. The new sensing mechanism is formed and it provides a new application of colloidal crystals in the sensing. 相似文献
19.
通过第一原理电子结构计算来研究有序多孔纳米网的电导特性变化的能带机理.能带结构分析结果表明:石墨烯纳米网超晶格(3m,3n)(m和n为整数)的电子本征态在布里渊区中心点发生四重简并;碳空位孔洞规则排列形成的石墨烯纳米网具有由简并态分裂形成的宽度可调带隙,无论石墨烯的两个子晶格是否对等.在具有磁性网孔阵列的石墨烯纳米网中,反铁磁耦合使对称子晶格的反演对称性增加了一项量子限制条件,导致能带结构在K点的二重简并态分裂成带隙.通过控制网孔密度能够有效调节石墨烯纳米网的带隙宽度,为实现新一代石墨烯纳米电子器件提供了理论依据. 相似文献
20.
Guang-cun SHAN 《Frontiers of Physics》2010,5(2):183
The fantastic physical properties of single-walled silicon nanotubes (SWSiNTs) under mechanical strain make them promising materials for fabricating nanoscale electronic devices or transducers. Here we investigate the energy band and band-gap properties of the SWSiNTs calculated from the tight-binding model approximation. The results show that the band-gap properties are very sensitive to the deformation degree and the helicity of the SWSiNTs. The results can be employed to guide the design of nanoelectronic devices based on silicon nanotubes. 相似文献