Mn掺杂ZnO纳米线磁性质的第一性原理研究

本文采用第一性原理方法系统研究了Mn原子单掺杂和双掺杂ZnO纳米线的稳定性和磁性质.所有掺杂纳米线的束缚能都为负值,表明掺杂增强了纳米线的稳定性.表面掺杂纳米线显示了直接带隙半导体特性,而中间掺杂纳米线显示了间接带隙半导体特性.纳米线的总磁矩主要来源于Mn原子3d轨道的贡献.由于杂化,相邻的O原子和Zn原子也产生了少量自旋.在超原胞内,Mn原子和O原子磁矩平行排列,表明它们之间是铁磁耦合.     

硫化锌纳米管稳定性、电子性质和磁性质的比较研究

用第一性原理方法系统地研究硫化锌纳米管的稳定性、电子性质和掺杂磁性质.比较三种纳米管的稳定性.研究表明,六边形截面的双壁管的稳定性最高,相同截面的单壁管稳定性次之,而圆截面的之字形和扶手椅纳米管稳定性最低.电子能带结构计算表明它们都是直接带隙半导体.纳米管表面氢吸附后,六边形截面的单壁管转变为间接带隙半导体.研究了磁性原子掺杂六边形截面管的磁性质.发现掺杂纳米管的形成能比纯纳米管的形成能低,说明掺杂过程是一个放热反应.纳米管的总磁矩等于掺杂的磁性原子的磁矩.这些单掺杂纳米管在可调磁的新材料方面有潜在的应用价值.     

表面氢化双层硅烯的结构和电子性质

采用密度泛函理论(DFT)广义梯度近似GGA和HSB06方法研究了氢化双层硅烯(silicene)的结构和电子性质, 结果表明: 氢化后的双层硅烯可能存在三种稳定的构型, AA椅型、AB椅型和AA船型, 其中AA椅型和AB椅型结构最为稳定, 氢化后这三种稳定构型材料的性质由零带隙的半金属(semimetal)转变为禁带宽度分别为1.208, 1.437和1.111 eV 的间接带隙的半导体, 采用混合泛函HSB06计算修正得到的带隙分别为1.595, 1.785 和1.592 eV. 进一步分析了在双轴应变下氢化双层硅烯的带隙随应变的关系, 得到应变可以连续的调节材料的带隙宽度, 这些性质有可能应用于未来的纳米电子器件.     

过渡金属 X（ X=Cr、Mn、Fe、Tc、Re ）掺杂Janus Ga2SSe 的第一性原理研究

利用密度泛函理论的第一性原理赝势平面波方法，研究过渡金属X(X=Cr、Mn、Fe、Tc、Re)原子掺杂Janus Ga₂SSe的磁性、电子性质及光学性质.研究表明：过渡金属掺杂Janus Ga₂SSe体系在Chalcogen-rich条件下有着比Ga-rich条件下更好的稳定性.其中Mn掺杂体系形成能在两种条件下皆为最低.本征Ga₂SSe是具有2.02 eV带隙的间接带隙半导体，在紫外区域有着很好的光伏吸收能力.与本征Ga₂SSe相比，Cr掺杂体系自旋向上通道出现杂质能级，自旋向上与向下通道不对称，呈磁矩为2.797μ_B铁磁性半金属. Mn掺杂体系在其自旋向上通道产生的杂质能级，呈磁矩为3.645μ_B的磁性P型半导体. Fe掺杂体系自旋向下通道产生的杂质能级，呈磁矩为3.748μ_B磁性P型半导体.在Tc与Re掺杂后，带隙皆由间接变直接带隙，呈无磁性的P型半导体.从光学性质来看，各掺杂体系与未掺杂Ga₂SSe在介电...     

单层haeckelites结构Ⅲ族金属硫族化合物MX(M=Al,Ga,In;X=S,Se,Te)

通过详尽的第一性原理计算,提出了一类新型的二维III族金属硫族化合物MX (M=Al, Ga, In; X=S,Se, Te)的同素异形体.这类化合物的结构是由正方形和八边形环构成的.计算得到的结合能和声子谱表明,所有的结构都同时具有能量和动力学稳定性.所有结构都是间接带隙半导体,其带隙大小随X原子由S到Se到Te的变化而减小.计算结果表明这类材料具有很广的带隙范围,从1.88到3.24 eV,同时它们的能带结构可以通过双轴应变进一步调节.这些结构具有丰富的电子结构性质和可调的带隙,有可能被用于未来纳米电子学领域.     

Co对单层MoS_2电子结构与磁性的影响

为了研究Co对单层MoS_2电子结构和磁性的影响,本文基于第一性原理,采用数值基组的方法计算了Co吸附式掺杂、Co替代式掺杂单层MoS_2的能带结构、态密度以及分析了其结构的稳定性.结果发现:Co替换式掺杂体系的形成能较低,实验上容易实现;Co在Mo位吸附的稳定性强于在S位吸附;Mo位吸附体系的总磁矩为0.999μB,其磁矩的主要来源于Co原子的吸附所贡献的0.984μB,Co原子的掺杂体系总磁矩为1.029μB,其磁矩的主要由Co原子替代掉一个Mo原子所贡献的磁矩为0.9444μB,相比于吸附体系,Co原子对磁矩的贡献率有所降低;无论是Co吸附在单层MoS_2表面还是Co直接替代掉Mo原子的掺杂体系,Co原子3d轨道的引入是引起单层MoS_2体系磁性的主要原因.     

含空位二维六角氮化硼电子和磁性质的密度泛函研究

基于密度泛函理论的第一性原理计算, 研究了含B原子空位(V_B), N原子空位(V_N), 以及含B–N键空位 (V_B+N)缺陷的二维氮化硼(h-BN)的电子和磁性质. 在微观结构上, V_B体系表现为在空位附近的N原子重构成等腰三角形, V_N体系靠近空穴的B 原子形成等边三角形, V_B+N体系靠近空穴处的B和N原子在h-BN平面上重构为梯形. 三种空位缺陷都使h-BN的带隙类型从直接带隙转变为间接带隙. V_B体系的总磁矩为1.0 μ_B, 磁矩全部由N原子贡献. 其中空穴周围的三个N原子磁矩方向不完全一致, 存在着铁磁性和反铁磁性两种耦合方式. 对于V_N 体系, 整个晶胞内的总磁矩也为1.0 μ_B, 磁矩在空穴周围区域呈现一定的分布. 关键词： 二维h-BN 空位 电子结构 磁性     

3d过渡金属元素掺杂Al12N12纳米线几何结构和电子性能的第一性原理研究

基于密度泛函理论的第一性原理计算方法,系统地研究了不同3d过渡金属元素(Sc、Ti、V、Cr、Mn、Fe、Co和Ni)掺杂Al₁₂N₁₂纳米线的几何结构、稳定性和电子结构.结果表明：所有掺杂体系均是热力学稳定的;掺杂Ni时体系保留了原有的非磁性间接带隙半导体特性;当掺杂其它原子(Sc、Ti、V、Cr、Mn、Fe、Co)时体系仍然保持为半导体,但带隙明显减小.掺杂过渡金属原子对于Al₁₂N₁₂纳米线的电子结构具有明显的调控作用,在能带调控和光电方面有潜在的应用前景.     

扶手椅型C3B纳米带:结构稳定性、电子特性及调控效应

单层C₃B是典型的类石墨烯二维材料,已在实验上成功制备.采用密度泛函理论方法(DFT)研究了扶手椅型单层C₃B纳米带的结构稳定性、电子性质及物理调控效应,计算结果表明:对于裸边纳米带,如果带边缘全由C原子组成(AA型),则电子相为半导体;两个带边缘均由C与B原子混合组成时(BB型),则纳米带的电子相为金属;而纳米带的一边由C原子组成、另一边由B与C原子混合构成(AB型),则纳米带的电子相为金属.这说明纳米带边缘的B原子对于纳米带成为金属或半导体起决定作用.而对于H端接的纳米带,它们全部为直接或间接带隙半导体.H端接的纳米带载流子迁移率一般比裸边纳米带低,这与它们较大的有效质量及较高的形变势有密切关系.同时发现半导体性质的纳米带对物理调控非常敏感,特别是在压应变和外电场作用下,纳米带的带隙明显变小,这有利于对光能的吸收和研发光学器件.     

带隙法测定SiGe/Si材料的应变状态

从固体模型理论的结果出发，计算了生长于Si（100）衬底上x值小于085的Si_1-xGe_x合金材料（能带结构为类Si结构）的间接带隙与应变的关系，结 果表明，应变的S iGe材料的带隙和完全弛豫状态下材料的带隙之差与应变呈线性关系.基于这一结果，提出了 用测量带隙来间接测定SiGe/Si应变状态的方法.用带隙法和x射线双晶衍射法测量了不同应 变状态下的SiGe/Si多量子阱材料的应变弛豫度，两者可以较好的符合，表明带隙法测量SiG e应变弛豫度是可行的. 关键词： SiGe合金 应变 带隙     

Transition metal encapsulated hydrogenated silicon nanotubes: Silicon-based half-metal

One-dimensional hydrogenated silicon nanotubes (H-SiNTs) with transition metal atom encapsulated were systematically studied by using density functional theory. The band structures and magnetic properties of the H-SiNTs can be tailored by doping transition metal (TM) (TM = Cr, Mn, Fe, Co) atoms within the tube. The hydrogenated silicon nanotubes are semiconductors with wide band gaps. TM doping turns H-SiNTs to be metals or semiconductors with a very small gap, and TM atoms at the center of the tubes keep large magnetic moments. Robust half-metallicity is observed in Mn-doped H-SiNTs and it is free from Peierls distortion. Thus, H-SiNTs with encapsulated magnetic elements may find important applications in spintronic devices.     

过渡金属原子掺杂的锯齿型磷烯纳米带的磁电子学特性

利用基于密度泛函理论的第一性原理方法,研究了掺杂铁、钴和镍原子的锯齿型磷烯纳米带(ZPNR)的磁电子学特性.研究表明,掺杂和未掺杂ZPNR的结构都是稳定的.当处于非磁态时,未掺杂和掺杂钴原子的ZPNR为半导体,而掺杂铁或者镍原子的ZPNR为金属.自旋极化计算表明,未掺杂和掺杂钴原子的ZPNR无磁性,而掺杂铁或者镍原子的ZPNR有磁性,但只能表现出铁磁性.处于铁磁态时,掺杂铁原子的ZPNR为磁性半导体,而掺杂镍原子的ZPNR为磁性半金属.掺杂铁或者镍原子的ZPNR的磁性主要由杂质原子贡献,产生磁性的原因则是在ZPNR中存在未配对电子.掺杂位置对ZPNR的磁电子学特性有一定的影响.该研究对于发展基于磷烯纳米带的纳米电子器件具有重要意义.     

A first principle study of hydrogenated graphdiyne

Based on recently synthesized two-dimensional graphdiyne, we have constructed several hydrogenated graphdiyne structures and studied their electronic structures and magnetic properties by first-principles calculations. Both direct and indirect band gap semiconductors are found in the nomagnetic hydrogenated configurations. Moreover, half semiconductors are found in the magnetic ground states of some hydrogenated graphdiyne structures we considered, although there is no transition metal element in the materials.     

Structural,electronic,and magnetic behaviors of 5d transition metal atom substituted divacancy graphene:A first-principles study

Structural, electronic, and magnetic behaviors of 5d transition metal(TM) atom substituted divacancy(DV) graphene are investigated using first-principles calculations. Different 5d TM atoms(Hf, Ta, W, Re, Os, Ir, and Pt) are embedded in graphene, these impurity atoms replace 2 carbon atoms in the graphene sheet. It is revealed that the charge transfer occurs from 5d TM atoms to the graphene layer. Hf, Ta, and W substituted graphene structures exhibit a finite band gap at high symmetric K-point in their spin up and spin down channels with 0.783 μB, 1.65 μB, and 1.78 μB magnetic moments,respectively. Ir and Pt substituted graphene structures display indirect band gap semiconductor behavior. Interestingly, Os substituted graphene shows direct band gap semiconductor behavior having a band gap of approximately 0.4 e V in their spin up channel with 1.5 μB magnetic moment. Through density of states(DOS) analysis, we can predict that d orbitals of 5d TM atoms could be responsible for introducing ferromagnetism in the graphene layer. We believe that our obtained results provide a new route for potential applications of dilute magnetic semiconductors and half-metals in spintronic devices by employing 5d transition metal atom-doped graphene complexes.     

Stability and electronic structure of InN nanotubes from first-principles study

The stability and electronic structure of hypothetical InN nanotubes were studied by first-principles density functional theory. It was found that the strain energies of InN nanotubes are smaller than those of carbon nanotubes of the same radius. Single-wall zigzag InN nanotubes were found to be semiconductors with a direct band gap while the armchair counterparts have an indirect band gap. The band gaps of nanotubes decrease with increasing diameter, similar to the case of carbon nanotubes.     

Strain effect on the electronic properties of 1T-HfS2 monolayer

We perform first-principles based on the density function theory to investigate electronic and magnetic properties of 1T-HfS₂ monolayer with biaxial tensile strain and compressive strain. The results show that HfS₂ monolayer under strains doesn’t display magnetic properties. When the strain is 0%, the HfS₂ monolayer presents an indirect band gap semiconductor with the band gap is about 1.252 eV. The band gap of HfS₂ monolayer decreases quickly with increasing compressive strain and comes to zero when the compressive strain is above −7%, the HfS₂ monolayer system turns from semiconductor to metal. While the band gap increases slowly with increasing tensile strain and comes to 1.814 eV when the tensile strain is 10%. By comparison, we find that the compressive strain is more effective in band engineering of pristine 1T-HfS₂ monolayer than the tensile strain. And we notice that the extent of band gap variation is different under tensile strain. The change of band gap with strain from 1% to 5% is faster than that of the strain 6–10%. To speak of, the conduction band minimum (CBM) is all located at M point with different strains. While the valence band maximum (VBM) turns from Γ point to K point when the strain is equal to and more than 6%.     

First-principles study of the structural, magnetic, and electronic properties of LiMBO3 (M = Mn, Fe, Co)

We present a first-principles calculation for the structural, magnetic, and electronic properties of LiMBO₃ (M = Mn, Fe, Co). Along the [0 0 1] direction, transition metals shows antiferromagnetic coupling in LiMBO₃ of both hexagonal and monoclinic lattices. The calculated magnetic moment of 5μB per formula unit is close to the experimental value. These compounds are semiconductors with band gap of 0.4-2 eV, and with average intercalation voltages of 2-4.8 V.     

Variation of the electronic properties of zigzag boron nitride nanotubes by Al-doping: a DFT study

Boron nitride nanotubes (BNNTs) are semiconductors with a wide band gap. In comparison with carbon nanotubes (CNTs), BNNTs have higher chemical stability, excellent mechanical properties and higher thermal conductivity. In this paper, we study the effect of diameters and substituting B and N atoms of various zigzag BNNTs with Al, on structural and electronic properties of BNNTs in solid state using the density functional theory method. The results of calculations of density of states and band structure (band) showed that the band gap between the valence and conduction level increases as a result of the enhancement of tube diameter of BNNTs. Finally, the results showed that the electronic properties of the pristine BNNTs can be improved by doping Al atom in the zigzag configuration of tubes.