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1.
We investigate the energy gaps and half-metallicity of the zigzag-edged β-graphyne nanoribbons via a tight-binding approach. In the presence of on-site Coulomb repulsion and proper transverse electric field strengths, the nanoribbons are forced into a half-metallic state by the electric field. A phase transition from half-metal to insulator is realized by changing the electric field or Coulomb potential. Both the electric field and Coulomb repulsion can open direct band gaps, resulting in a metal-insulator phase transition. The band gaps oscillate with the electric field, contrary to linear change with the Coulomb potential.  相似文献   
2.
《Physics letters. A》2020,384(24):126453
In this article, we study the exchange coupling interactions of the equiatomic quaternary Heusler alloy CoFeTiSn, using the two methods: Monte Carlo simulations and the ab-initio method. In a first step, we use the ab-initio calculations to investigate the structural, the electronic and the magnetic properties of this alloy under the GGA method. The analysis of the energy dependence on the lattice parameter a (Å) of the equiatomic quaternary Heusler alloy CoFeTiSn, is discussed for different atomic configurations. The ferromagnetic configuration is found to be the more stable one, with an optimal lattice parameter value 6.00 Å. On the other hand, the electronic structure results show that the compound CoFeTiSn exhibits a half-metallic character and a spin polarization of 100% at the Fermi-level. The total magnetic moment of this alloy is found to be equal to 2.00 μB which follows the Slater Pauling rule. Our results support the half-metallic behavior of the studied material. In order to complete this study, we reported the dependence of the critical transition temperature as a function of the parameter α of the equiatomic quaternary Heusler alloy CoFeTiSn. We showed that the critical temperature increases almost linearly with an increase of the values of the parameter α.  相似文献   
3.
First-principle calculations have been performed to study the sensing of CO gas in various considered configurations. The adsorption of CO on zigzag BN nanoribbon (ZBNNR) and zigzag AlN nanoribbon (ZAlNNR) was modelled in five different possibilities. The effect of CO adsorption is to reduce the band gap in both types (BN/AlN) of the nanoribbons. Interestingly, a finite magnetic moment (0.96 μB for ZBNNR and 0.69 μB for ZAlNNR) has been obtained which depends upon the adsorption configuration of CO. Half-metallicity was also observed upon selective CO adsorption on ZAlNNR irrespective of the ribbon width. Present findings suggest that CO gas molecules could be detected through adsorption on BN/AlN nanoribbons via changes in electronic and/or magnetic properties.  相似文献   
4.
利用第一性原理计算了Inverse-Heusler合金Ti_2Co_(1-x)Ni_xGa的半金属性、磁性和电子性质.计算结果表明Ti_2Co_(1-x)Ni_xGa的原胞总磁矩和晶格常数随着x的增加而增加.由于过渡金属原子之间的直接杂化和sp电子的调节,原胞总磁矩和晶格常数随掺杂浓度x的改变而改变,并与Slater Pauling规则形成一定的差异.当Ni的掺杂浓度x=0.5时,Ti_2Co_(1-x)Ni_xGa合金的费米面在自旋向下带隙的中间位置,因而可以判定Ti2Co0.5Ni0.5Ga将具有最佳的半金属稳定性.  相似文献   
5.
基于密度泛函理论的GGA计算,我们具体研究了Hg2 CuTi型Heusler合金Ti2 FeB的电子结构和磁性质,结果发现Ti2FeB合金在其费米面处存在100%的自旋极化,并在5.1~6.2(A)晶格范围内被保留.Ti2FeB具有大约0.5 eV的半金属带隙和1μB的原胞总磁矩,是一个稳定的半金属铁磁体.此外,我们的研究也表明RKKY型间接交换和d电子杂化在决定合金磁性质中起决定性作用.  相似文献   
6.
All electron full potential calculations based on spin density functional theory are performed to study cubic zincblende (ZB) and hexagonal NiAs structures of bulk CrTe, free (0 0 1) surfaces of ZB CrTe, and interface of ZB CrTe with ZnTe(0 0 1). The ferromagnetic NiAs structure is reported to be about 0.26 eV more stable than the ferromagnetic ZB phase while ZB CrTe is found to be a half-metallic ferromagnet with a half-metallic gap of about 2.90 eV. Thermodynamic stability of CrTe(0 0 1) surfaces are studied in the framework of ab-initio thermodynamic. The obtained phase diagram evidences more stability of the Te terminated surface compared with the Cr termination. We discuss that both Te and Cr ideal terminations of CrTe(0 0 1) retain bulk-like half-metallic property but with a reduced half-metallic gap compared with bulk value. The structural, electronic, magnetic, and band alignment properties of the ZB CrTe/ZnTe(0 0 1) interface are computed and a rather large minority valence band offset of about 1.09 eV is observed in this heterojunction.  相似文献   
7.
通过基于密度泛函理论的第一原理计算,优化了纤锌矿结构的化合物TmZn15S16(Tm=V,Cr,Mn)的几何结构,并研究了它们的磁学性能.结果表明:TmZn15S16均为典型的半金属铁磁体,它们的超胞磁矩分别为3.0099μB,3.9977μB和5.0092μB;这些磁矩主要来源于被掺入的过渡元素;CrZn15S16的半金属特性比VZn15S16和MnZn15S16更稳定;这些半金属铁磁体的半金属带隙均比较宽,表明它们可能具有较高的居里温度;TmZn15S16中杂质过渡离子的电子结构分别为V:eg2↑t12g↑,Cr:eg2↑t22g↑和Mn:eg2↑t32g↑.  相似文献   
8.
First-principles full-potential linearized augmented plane-wave method is used to investigate the electronic structure and magnetic properties of hypothetical zinc-blende and rocksalt LiS, NaS and KS. We find that all the compounds except rocksalt LiS exhibit half-metallic ferromagnetism with an integer magnetic moment of 1.00 μB per formula unit. The ferromagnetism results from the spin-polarization of p states of anion S. Total energies calculations indicate the rocksalt phase is lower in energy than the zinc-blende one. The total energy differences are about 0.38, 0.36 and 0.32 eV per formula unit for LiS, NaS and KS, respectively. Meanwhile, it is shown that rocksalt NaS and KS have the half-metallic gaps of 0.22 and 0.41 eV, respectively, and the half-metallic gaps are 0.03, 0.46 and 0.65 eV for zinc-blende LiS, NaS and KS, respectively. We also find the half-metallicity is robust against the lattice contraction up to 7% and 13% for rocksalt NaS and KS, respectively. Although rocksalt LiS is nonmagnetic and metallic at the equilibrium lattice constant, it shows half-metallic ferromagnetism when the lattice constant is larger than 5.40 Å.  相似文献   
9.
Pseudopotentials and plane-wave basis set method is used to investigate the electronic structure and magnetic properties for state-of-the-art zinc-blende and rocksalt M N (M=K, Na) alloys. We find that these compounds exhibit half-metallic characters with an integer magnetic moment of 2.00μB. The half-metallic properties result from a fully spin-polarization of s and p states. The origin of energy gap mainly comes from the hybridization both s and p states. Total energies calculations indicate the rocksalt phase is lower in energy than the zinc-blende one. The difference of total energy are about 0.035 Ry per formula unit for KN and NaN, respectively. For these compounds, Slater-Pauling curve Mt=(Zt−4) (in μB unit) is obeyed between valence electrons and total magnetic moment. Meanwhile, we also find the preservation of half metallic characters when the lattice parameter is moderate compressed.  相似文献   
10.
本文构建了half-Heusler合金CoVTe和FeVTe.运用基于第一性原理的全势能线性缀加平面波方法,计算half-Heusler合金CoVTe和FeVTe的电子结构.电子结构的自旋极化计算结果表明,合金CoVTe和FeVTe具有半金属性,它们的半金属隙分别为0.21 eV和0.20 eV.磁性计算结果显示,合金CoVTe和FeVTe的晶胞总磁矩分别为2.00μ_B和1.00μ_B;合金晶胞中过渡金属V具有较强的原子磁矩,Te的原子磁矩较弱,而且为负值.使合金晶格均匀形变△a/a_0在±7%的范围内变化,分别计算CoVTe和FeVTe的电子结构.计算结果表明,晶格均匀形变△a/a_0分别为-7%—+7%和-4.8%—+7%时,合金CoVTe和FeVTe仍然保持半金属性,并且晶胞总磁矩分别稳定于2.00μ_B和1.00μ_B.  相似文献   
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