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...     

Mn/C共掺杂ZnS纳米管磁性质研究

采用第一性原理密度泛函理论系统地研究Mn原子单掺杂和双掺杂ZnS纳米管的结构、电子性质和磁性质.掺杂纳米管的形成能比纯纳米管形成能更低,表明掺杂是个放热过程.掺杂纳米管的能隙远小于纯纳米管能隙.计算结果表明Mn掺杂纳米管趋于反铁磁态.为了获得室温铁磁性,用一个C原子替代一个S原子.发现铁磁态能量比反铁磁态能量低0.454 eV.如此大的能量差表明这类材料中有可能获得室温铁磁性.     

Fe掺杂单壁ZnS纳米管磁性质

采用第一性原理密度泛函理论系统研究Fe原子掺杂单壁ZnS纳米管的结构和磁性质.首先比较掺杂纳米管的稳定性.结果表明,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.单掺杂纳米管的总磁矩等于掺杂的磁性原子的磁矩,主要来自Fe原子3d态的贡献.Fe原子掺杂单壁ZnS纳米管趋向于反铁磁态.为了得到稳定的铁磁态,用一个C原子替代掺杂体系中的一个S原子.计算发现铁磁态的能量比亚铁磁态低0.164 eV的.在铁磁态和反铁磁态之间存在的巨大的能量差,表明此掺杂体系可能获得室温铁磁性.     

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.     

P掺杂硅纳米管电子结构与光学性质的研究

采用基于密度泛函理论的第一性原理计算,研究了P掺杂对单壁扶手型硅纳米管电子结构和光学性质的影响.结果表明:经过P掺杂,单壁扶手型硅纳米管的能带结构从间接带隙变为直接带隙,其价带顶主要由Si-3p态电子构成,导带底主要由Si-3p态电子和Si-3s态电子共同决定;同时通过P掺杂,使单壁扶手型硅纳米管的禁带宽度变窄,导电性增强,吸收光谱产生红移.研究结果为硅纳米管在光电器件方面的应用提供了理论基础.     

过渡金属元素X（X=Mo，Tc，Ru）掺杂单层GaS的第一性原理研究

近年来，二维GaS由于其优异的性质引起了科研人员的关注.基于密度泛函理论计算了过渡金属元素X(X=Mo, Tc, Ru)掺杂单层二维GaS的电子结构、磁性性质及光学性质.计算结果表明：单层GaS材料为间接带隙的非磁性半导体，在对S位点进行替位式掺杂后，Ga-rich和S-rich条件的形成能均为正数，导致过渡金属元素Mo、Tc和Ru不能自发地进入进入单层GaS材料中.所有掺杂体系都引入了杂质能级，杂质能级主要由掺杂原子的4d轨道贡献.掺杂后所有体系的带隙都有所减小，上自旋和下自旋的能带结构不再对称，使得Mo掺杂体系呈现半金属铁磁性，Tc和Ru掺杂体系呈磁性半导体特性，Mo、Tc和Ru掺杂后的总磁矩分别为4μ_B, 3μ_B和2μ_B,磁矩主要由掺杂原子的局域磁矩产生.掺杂后单层GaS的静介电常数得到提高，吸收谱出现红移，在可见光区和近红外区的吸收系数变大，对可见光的利用率增强.     

Mn/C共掺杂ZnS纳米管磁性质研究（英文）

采用第一性原理密度泛函理论系统地研究Mn原子单掺杂和双掺杂ZnS纳米管的结构、电子性质和磁性质.掺杂纳米管的形成能比纯纳米管形成能更低,表明掺杂是个放热过程.掺杂纳米管的能隙远小于纯纳米管能隙.计算结果表明Mn掺杂纳米管趋于反铁磁态.为了获得室温铁磁性,用一个C原子替代一个S原子.发现铁磁态能量比反铁磁态能量低0.454 e V.如此大的能量差表明这类材料中有可能获得室温铁磁性.     

C在不同位置掺杂(n,n)型BN纳米管的密度泛函研究

用密度泛函B3LYP/3-21G(d)方法,并利用周期边界条件,研究了C原子在不同位置掺杂的(n,n)型BN纳米管的结构与性质.揭示了几何结构特征、能量、稳定性和能带结构的变化规律.研究了C原子在B位或N位置分别掺杂的BN纳米管的模型(掺杂浓度x=1/(4n),n=3—9),部分B位掺杂管发生了变形,而所有N位掺杂管则几乎不变形,而且N位比B位的掺杂能更低(管更稳定),B位掺杂管的能隙为1.054—2.411 eV,N掺杂管的能隙为0.252—1.207 eV,所有掺杂管都是半导体,所有掺杂管都具有直接带隙.     

Ga空位对GaN:Gd体系磁性影响的第一性原理研究

采用基于密度泛函理论的第一性原理结合投影缀加平面波的方法,研究了GaN中Ga被稀土元素Gd替代以及与邻近N或Ga空位组成的缺陷复合体的晶格常数、磁矩、形成能以及电子结构等性质.结果发现,Gd掺杂GaN后禁带宽度变窄,由直接带隙半导体转为间接带隙半导体;单个Gd原子掺杂给体系引入大约7μB的磁矩;在Gd与Ga或N空位形成的缺陷复合体系中,N空位对引入磁矩贡献很小,大约0.1μB,Ga空位能引入约2μB的磁矩.随着Ga空位的增多,体系总磁矩增加,但增加量与Ga空位的位置分布密切相关.当Ga空位分布较为稀疏时,Gd单原子磁矩受影响较小,但当Ga空位距离较近且倾向于形成团簇时,Gd单原子磁矩明显增加,而且这种情况下空位形成能也最小.     

Cr掺杂ZnO纳米线电子性质和磁性质

本文采用第一性原理密度泛函理论系统的研究了Cr原子单掺杂和双掺杂两种尺寸ZnO纳米线的电子性质和磁性质.所有掺杂纳米线的形成能都比纯纳米线的形成能低,表明掺杂增强了纳米线的稳定性.研究发现Cr原子趋于替代纳米线表面的Zn原子.所有掺杂纳米线都显示了金属性.纳米线的总磁矩主要来源于Cr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,Cr和O原子磁矩反平行排列,表明它们之间是反铁磁耦合.表面双掺杂纳米线铁磁态能量比反铁磁态能量低149 meV,表明Cr掺杂ZnO纳米线可能获得室温铁磁性.     

Electronic structure and magnetic properties of substitutional transition-metal atoms in GaN nanotubes

The electronic structure and magnetic properties of the transition-metal(TM) atoms(Sc–Zn, Pt and Au) doped zigzag GaN single-walled nanotubes(NTs) are investigated using first-principles spin-polarized density functional calculations. Our results show that the bindings of all TM atoms are stable with the binding energy in the range of 6–16 eV. The Sc- and V-doped GaN NTs exhibit a nonmagnetic behavior. The GaN NTs doped with Ti, Mn, Ni, Cu and Pt are antiferromagnetic. On the contrary, the Cr-, Fe-, Co-, Zn- and Au-doped GaN NTs show the ferromagnetic characteristics. The Mn- and Codoped GaN NTs induce the largest local moment of 4μB among these TM atoms. The local magnetic moment is dominated by the contribution from the substitutional TM atom and the N atoms bonded with it.     

Quantum chemical simulations of titanium dioxide nanotubes used for photocatalytic water splitting

Titanium dioxide nanotubes (NTs) built from various initial 2D models of TiO2 (a promising catalyst for water splitting) are investigated via density functional theory using the B3LYP hybrid exchange-correlation functional in the localized basis set of a linear combination of atomic orbitals. For TiO₂ NTs (eight different types of morphology) created from four initial 2D structures, full geometry optimization is performed and the main energy parameters, such as the band gap width, energy positions of the valence band top and the conduction band bottom, and NT formation and strain energy, are calculated. Analysis of the NT strain and formation energies enables us to choose their most stable configuration, which can further be employed to simulate NTs doped with impurity atoms capable of serving as efficient centers for the photocatalytic dissociation of water molecules.     

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.     

First-principles study on the magnetic property of C-doped wurtzite ZnS

We have studied the structure, electronic and magnetic properties of wurtzite (WZ) ZnS semiconductor doped with one or two C atoms using first-principles calculations. The moderate formation energy implied that C-doped ZnS could be fabricated experimentally. The total magnetic moment of the 72 atom super cell was 2.02μB, mainly due to the 2p component of the C atom. Electronic structures showed ZnS doped with C atom was p-type half-metallic ferromagnetic (FM) semiconductor and hole mediation was responsible for the ferromagnetism. The large energy difference (154 meV) between the FM and antiferromagnetic (AFM) state implied room-temperature ferromagnetism for C-doped WZ ZnS, which has great potential in spintronic devices.     

Modulation of magnetic properties of bilayer SnSe with transition-metals doping in the interlayer

We investigate the spin-polarized electronic and magnetic properties of bilayer SnSe with transition-metal (TM) atoms doped in the interlayer by using a first-principles method. It shows that Ni dopant cannot induce the magnetism in the doped SnSe sheet, while the ground state of V, Cr, Mn, Fe and Co doped systems are magnetic and the magnetic moment mainly originates from 3d TM atom. Two types of factors, which reduce the magnetic moment of TM atoms doped in bilayer SnSe, are identified as spin-up channel of the 3d orbital loses electrons to SnSe sheet and spin-down channel of the 3d orbital gains electrons from 4s orbital. The spin polarization is found to be 100% at Fermi level for the Mn and Co atoms doped system, while the Ni-doped system is still a semiconductor with a gap of 0.26 eV. These results are potentially useful for development of spintronic devices.     

Investigation and simulation of the structural and electronic properties of LiF:Mg,LiF:Cu,LiF:P nano-layer dosimeters

In this study, electronic structure of lithium fluoride thin films in pure state and doped with magnesium (Mg), copper (Cu) and phosphorus (P) impurities was studied using WIEN2K Code. The structural and electronic properties of two LiF thin films with 1.61 and 4.05?nm thicknesses were studied and compared. Results show that the distance of atoms in the surface and central layers of pure LiF are 1.975 and 2.03?nm, respectively. Electronic density of the valence band around the surface atoms is greater than that around middle atoms of the supercell. The band gap of bulk LiF is 9?eV. But, in the case of thin films, it is reduced to 2?eV. Electronic and hole-traps were not observed in composition of LiF thin films doped with Mg and P with 1.61 and 4.05?nm thickness and in fact, metallic properties were observed. When Cu atoms were doped in composition of an LiF thin film, the thin film was converted to semiconductor.     

过渡金属TM(V,Cr,Mn)掺杂ZnS的电子结构和磁性

采用基于密度泛函理论(DFT)的第一性原理赝势平面波方法,对过渡金属V、Cr、Mn 掺杂ZnS的超晶胞体系进行了几何结构优化,计算了晶格常数、电子结构与磁学性质。研究结果表明：掺入V,Cr后,ZnS表现出明显的半金属性,而掺入Mn后,半金属性不明显;掺入过渡金属TM(V,Cr,Mn)后系统产生的磁矩主要有杂质的3d态电子贡献,且磁矩的大小与过渡金属的电子排布有关。