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1.
It has been demonstrated that the mechanical and electronic properties of materials change significantly when the external dimension are confined to the nanoscale. Consequently, one-dimensional (1D) transition-metal dichalcogenide (TMDC) nanotubes (NTs), obtained from scrolling two-dimensional (2D) TMDC, have attracted much attentions because of their intriguing properties wherein the chirality of NTs plays a key role in affecting the electronic properties. Taking into the amount of speculations on the mechanism and the increasing needs for better device design and performance control, understanding the effect of chirality on the electronic properties is timely and relevant. Here, MoS2 NTs are comprehensively studied by first-principles calculations. The results show that the armchair (6≤ch≤14) exhibits the indirect-band-gap and zigzag (10≤ch≤20) with direct-band-gap. Moreover, the carrier mobility is enhanced with the decrease of radial length, in accord with the smaller effective mass of hole and electron for both types NTs. Finally, the formation energy showed that the smaller the radial diameters is, the harder the NTs is to form. Moreover, the similarity of lattice parameters and formation energy implies a potential possibility of transition between two types of NTs with low index chiral vectors, such as ANT(6,6)/ZNT(10,0). 相似文献
2.
Using first-principles calculations based on the density functional theory, we study the effect of strain on the electronic and magnetic properties of Cr-doped WSe2 monolayer. The results show that no magnetic moment is induced in the Cr-doped WSe2 monolayer without strain. For the Cr substitutions, the impurity states are close to the conduction bands, which indicate n-type doping occurs in this case. Then we applied strain (from −10% to 10%) to the doped system, and find that a little magnetic moment is induced with tensile strain from 6% to 9% and negligible. We find that the influence of strain on the magnetic properties is inappreciable in Cr-doped WSe2. Moreover, the tensile strain appears to be more effective in reducing the band gap of Cr-doped WSe2 monolayer than the compressive strain. 相似文献
3.
《Physics letters. A》2020,384(24):126575
Inspired by MoS2-OH bilayer framework (Zhu et al. 2019 [19]), first principles calculations are applied to explore its possible configurations as well as their electronic and transport properties. The calculated results indicate O-MoS2 and OH…O-MoS2 are two primary configuration in MoS2-OH bilayer. It shows negligible difference in electronic structure between O-MoS2 and pure MoS2, but a flat band arise at the Fermi level in OH…O-MoS2. Their contact characteristics show larger binding energy with selected metals and smaller contact barrier with Pt electrode. Besides, the currents of both O-MoS2 and OH…O-MoS2 are enlarged compared with that of pure MoS2 in finite bias, indicating MoS2-OH bilayer may be potential candidate for future electron device applications. 相似文献
4.
《Physics letters. A》2014,378(38-39):2910-2914
We present first principles theory calculations about the chirality and vacancy effects of the mechanical and electronic properties of monolayer MoS2. In the uni-axial tensile tests, chirality effect of the mechanical properties is negligible at zero strain and becomes significant with the increasing strain, regardless of vacancies. The existence of vacancies decreases the Young's modulus and ultimate strength of the MoS2 structure. During the uni-axial tensile tests, the band gap decreases with the increasing strain, regardless of chirality and vacancies. The band gap is reduced with the intermediate state brought by the existence of vacancies. No chirality effect can be observed on the band gap variations of perfect MoS2. Chirality effect appears to the band gap variation of defected MoS2 due to the local lattice relaxation near the vacancies. 相似文献
5.
Seifert G Terrones H Terrones M Jungnickel G Frauenheim T 《Physical review letters》2000,85(1):146-149
Structural and electronic properties as well as the stability of MoS2 nanotubes are studied using the density-functional-based tight-binding method. It is found that MoS2 zigzag ( n,0) nanotubes exhibit a narrow direct band gap and MoS2 armchair ( n,n) possess a nonzero moderate direct gap. Interestingly, the ( n,n) tubes show a small indirect gap similar to the direct gap of ( n,0) nanotubes. Simulated electron diffraction patterns confirm the existence of armchair and zigzag disulphide nanotubes. The structure of the MoS2 nanotube tips is explained by introducing topological defects which produce positive and negative curvature. 相似文献
6.
本文利用第一性原理计算讨论了硫族元素掺杂单层Ag2S的缺陷形成能和电子性质.缺陷形成能反映了在富Ag条件下的掺杂更容易.计算得到的带隙、Mulliken布居和态密度展示出了其相应结构的电子性质.与纯单层的Ag2S相比,Se/Te掺杂Ag2S后的带隙显示出其电导率变化不大.基于Mulliken原子和键布居,研究了硫族元素掺杂后Ag2S中的共价性.此外,通过讨论态密度,分析了能级的移动和电子的贡献. 相似文献
7.
Through the first principle calculation, electronic properties of monolayer MoS2 doped with single, double, triple and tetra-atoms of P, Cl, O, Se at the surface S site are discussed. Among the substitutional dopant, our calculation results show that when P atoms are doped on a monolayer MoS2, a shift in the Fermi energy into the valence band is observed, making the system p-type. Meanwhile, band gap gradually decreases as increasing the number of P atoms. On the contrary, Cl is identified as a suitable n-type dopant. It is observed that Cl for initial three dopant behaved as magnetic and afterwards returned to non-magnetic behavior. The band gap of the Cl doped system is also dwindling gradually. Finally, O and Se doped systems have little effect on electronic properties near band gap. Such doping method at the S site, and the TDOS and PDOSs of each doping system provide a detailed of understanding toward working mechanism of the doped and the intrinsic semiconductors. This doping model opens up an avenue for further clarification in the doping systems as well as other dopant using this method. 相似文献
8.
First-principles study of nanotubes within the tetragonal,hexagonal and dodecagonal cycle structures
A systematic study has been done on the structural and electronic properties of carbon, boron nitride and aluminum nitride nanotubes with structure consisting of periodically distributed tetragonal (T ≡A2X2), hexagonal (H ≡A3X3) and dodecagonal (D ≡A6X6) (AX=C2, BN, AlN) cycles. The method has been performed using first-principles calculations based on density functional theory (DFT). The optimized lattice parameters, density of state (DOS) curves and band structure of THD-NTs are obtained for (3, 0) and (0, 2) types. Our calculation results indicate that carbon nanotubes of these types (THD-CNTs) behave as a metallic, but the boron nitride nanotubes (THD-BNNTs) (with a band gap of around 4 eV) as well as aluminum nitride nanotubes (THD-AlNNTs) (with a band gap of around 2.6 eV) behave as an semiconductor. The inequality in number of atoms in different directions is affected on structures and diameters of nanotubes and their walls curvature. 相似文献
9.
《Current Applied Physics》2015,15(9):970-976
The mechanical and thermodynamic properties, chemical bonding characteristics and electronic structure of Nb2MB2 (M = Mo, W, Re or Os) with a new tetragonal U3Si2-type superstructure (space group P4/mnc, no. 128) were studied by means of density functional theory calculations. All Nb2MB2 structures studied were demonstrated to be thermodynamically and mechanically stable. The bulk, shear and Young's moduli, Poisson's ratio, Debye temperature and anisotropy factors were derived for ideal polycrystalline Nb2MB2 aggregates. Among these compounds, Nb2WB2 was found to have the highest shear modulus and hardness. The electronic densities of state and electronic localization function analysis revealed the metallicity and strong covalent B–B, Nb–B and M−B bonding in Nb2MB2. Moreover, these results reveal that the covalence between Nb 4d, M nd (n = 4 for Mo and 5 for W, Re and Os) and B 2p states is the cause of the relatively higher elastic modulus and hardness of the Nb-based compounds. Finally, thermodynamic properties, including the bulk modulus, heat capacity and thermal expansion coefficient of Nb2WB2 were obtained systematically under high temperature and pressure. 相似文献
10.
E. Megıas E. Ruiz Arriola L. L. Salcedo 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):553-556
We address a possible relation between the expectation value of the Polyakov loop in pure gluodynamics and full QCD based
on Polyakov Chiral Quark Models where constituent quarks and the Polyakov loop are coupled in a minimal way. To this end,
we use a center symmetry-breaking Gaussian model for the Polyakov loop distribution which accurately reproduces gluodynamics
data above the phase transition in terms of dimension-2 gluon condensate. The role played by the quantum and local nature
of the Polyakov loop is emphasized. 相似文献
11.
Besbes Anissa Djelti Radouan Bestani Benaouda Akel Omar 《Chinese Journal of Physics (Taipei)》2018,56(6):2926-2936
This work concerns a predictive study of PdZrGe half-Heusler compound with 18 valence electrons. The structural and electronic properties are investigated by using the full potential linearized augmented plane wave (FP-LAPW) method within the framework of generalized gradient approximation (GGA). To investigate the thermodynamic properties, we are applying the quasi-harmonic Debye model. The semi-classical Boltzmann theory as implemented in the BoltzTraP code is used to study the thermoelectric properties. We have found that the PdZrGe alloy is an indirect band gap semiconductor. Also the PdZrGe exhibit a negative thermal expansion. The Seebeck coefficient (S) is relatively high (237 µV/K at 300?K) due to its semiconducting nature. The calculated thermoelectric figure of merit is 0.759 at 300?K; this result indicates that our compound is an excellent candidate for practical applications in the thermoelectric field. 相似文献
12.
CO、C2H2、CH4是溶解在变压器油中的典型故障特征气体,其种类和浓度能够反映油浸式变压器绝缘故障的不同类型和严重程度,进行油中溶解气体分析是在线检测变压器运行状态的重要方法.基于第一性原理,通过Mn-MoS2单层对三种气体的吸附能、转移电荷、态密度和形变电荷密度等参数以及解吸性能分析和灵敏度计算,提出了一种基于Mn-MoS2材料的气敏传感器对油中溶解气体进行分析的方法.结果表明Mn-MoS2对CH4是物理吸附,对CO和C2H2是化学吸附.对于Mn-MoS2来说,CH4在常温下吸附能力差且灵敏度低,CO在不同温度下均有较强的吸附能力,而C2H2在常温下吸附稳定,高温下易解吸且响应灵敏度高.因此,Mn掺杂的MoS2体系可预期作为CO的气体吸附剂和检测C2H 相似文献
13.
In the present work, the structural, electronic, elastic and mechanical properties of Ti2AlC and Ti2Al(C1-xOx) solid solutions were investigated using first-principles calculations for varied O content incorporation (x = 0, 0.125, 0.25, 0.375, 0.5). According to the calculation results, all Ti2Al(C1-xOx) solid solutions with various x values are stable, and the bonding strength of the Ti–Al bond increases with the doping of O element. In addition, the shear modulus G and C44 elastic constant of Ti2Al(C1-xOx) solid solutions are both lower than the bulk modulus B, indicating that the phase has good damage tolerance. Not only that, compared with Ti2AlC, the plasticity and toughness of Ti2Al(C1-xOx) solid solutions are improved with the increase of O atom doping and doping ratio. Simultaneously, the doping of O atom is also beneficial to reduce the generalized stacking fault energy of Ti2AlC, making the Ti2Al(C1-xOx) solid solutions more prone to shear deformation, thereby further enhancing plasticity. 相似文献
14.
二硒化钼的层间相互作用强,单层结构具有更低的带隙和更好的稳定性.由于独特的光学性质和优异的电学性能受到研究人员的广泛关注.本文基于密度泛函理论的第一原理,计算和分析了在双轴拉伸压缩应变条件下单层MoSe2能带结构,拉曼光谱和声子谱的变化规律以及性质产生的原因.在拉伸压缩应变作用下,直接带隙转变为间接带隙.当拉伸应变达到12%时,材料发生半导体-金属相变.当压缩应变达到6%时,声子谱中开始出现虚频率,表明结构开始变得不稳定. 相似文献
15.
Mosayeb Naseri 《Physics letters. A》2018,382(10):710-715
In this paper, by using of the first principles calculations in the framework of the density functional theory, we systematically investigated the structure, stability, electronic and optical properties of a novel two-dimensional pentagonal monolayer semiconductors namely penta-SiC5 monolayer. Comparing elemental silicon, diamond, and previously reported 2D carbon allotropes, our calculation shows that the predicted penta-SiC5 monolayer has a metastable nature. The calculated results indicate that the predicted monolayer is an indirect semiconductor with a wide band gap of about 2.82 eV by using Heyd–Scuseria–Ernzerhof (HSE06) hybrid functional level of theory which can be effectively tuned by external biaxial strains. The obtained exceptional electronic properties suggest penta-SiC5 monolayer as promising candidates for application in new electronic devices in nano scale. 相似文献
16.
《Physics letters. A》2020,384(24):126569
The electronic structure and quantum transport properties of pristine armchair graphene nanoribbons (AGNRs) and AGNRs adsorbing super-halogen LiF2 and super-alkaline Li3 clusters (Li3/AGNRs/LiF2) were investigated using density functional theory and non-equilibrium Green's function calculations. It was found that LiF2 and Li3 clusters are stably adsorbed on the AGNRs, and the adsorption of Li3 and LiF2 endows AGNRs with the characteristics of n-type and p-type semiconductors, respectively. The Li3/AGNRs/LiF2 structure reduces the band gap and the turn-on voltage, and improves the transmission coefficient of the ANGRs device. This structure also exhibit the rectification characteristics of a pn junction with the forward bias current greater than the reverse bias current. This shows that adsorption of super-alkali and super-halogen clusters in different regions of AGNRs is a feasible approach for obtaining AGNRs with pn junction characteristics. 相似文献
17.
First principles calculations of the adsorption and diffusion of Y on the Si(0 0 1)-c(4 × 2) surface
We have studied the adsorption and diffusion of yttrium on the Si(0 0 1)-c(4 × 2) surface in the early stages of growth. Our first principles total energy calculations are based on the density functional theory as implemented in the SIESTA code. The exchange and correlation energies are treated within the generalized gradient approximation according to the Perdew, Burke and Ernzerhof parametrization. Our results demonstrate that the most favorable adsorption site is in the trench between two silicon dimer rows, identified as valley-bridge (V). Our studies show that the diffusion of an Y adatom on Si(0 0 1)-c(4 × 2) surface presents an anisotropic behavior. We found two values for the barriers along the valley (0.54 and 1.07 eV) and one of 1.24 eV in the perpendicular direction, showing that diffusion along the valley is more probable. The analysis of the Mulliken overlap populations shows that the bonding between an Y adatom and the surface is partially covalent. Two Y atoms on the surface do not form dimers instead they are adsorbed as adatoms. 相似文献
18.
张丽 《原子与分子物理学报》2016,33(6):1126-1130
本文从第一性原理出发,基于密度泛函理论体系下的广义梯度近似(GGA)方法,对不同压力下YB_6的电子结构及光学性质方面进行了研究.结果表明:在一定的压力范围内随着压力的增大,费米面以上的能带往高能量处移动,费米面以下的能带往低能量处移动.能量损失谱的第一个峰随着压力的增大往高能量处移动,并且峰强增大.这表明可以通过压力来调节YB_6在可见光区的吸收谷的位置及强度,在高压下YB_6将展现更好的隔热性能. 相似文献
19.
张丽 《原子与分子物理学报》2018,35(6)
本文从第一性原理出发,基于密度泛函理论体系下的广义梯度近似(GGA)方法,对不同压力下YB6的电子结构及光学性质方面进行了研究。结果表明:在一定的压力范围内随着压力的增大,费米面以上的能带往高能量处移动,费米面以下的能带往低能量处移动。能量损失谱的第一个峰随着压力的增大往高能量处移动,并且峰强增大。这表明可以通过压力来调节YB6在可见光区的吸收谷的位置及强度,在高压下YB6将展现更好的隔热性能。 相似文献
20.
采用密度泛函理论对M-(Sm、Pr、Ga)掺杂锐钛矿型TiO2能带和电子性质进行了系统的理论研究. 计算结果表明,通过Sm和Pr的掺杂可以降低TiO2的带隙进而使其产生吸收边红移,通过Ga的掺杂能使带隙稍增加. 这主要是由于Sm和Pr的掺杂使Sm和Pr上的4f层电子与原子相邻O原子上的2p层电子相互作用,形成的杂质能级影响了Ti-O的能带结构,从而降低带隙,提高TiO2的可见光吸收性能. 相似文献