共查询到19条相似文献,搜索用时 250 毫秒
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采用基于密度泛函理论(DFT)的第一性原理计算研究了 (Ba0.5Sr0.5)TiO3 (BST) 晶体在高压下的电子结构及能带变化行为. 研究结果发现,随着压强的增加,BST能带间隙先增加,在压强为55 GPa时达到最大值,然后减小,这些有趣的结果将有助于开发与设计新的BST铁电器件. 进一步地,通过电子态密度和密度分布图的研究分析可知:在低压区域(0
55 GPa),则是出现的离域现象占主导(电子的离域作用超过键态的作用),从而使带隙减小. 关键词: 钛酸锶钡 第一性原理 高压 能带间隙 相似文献
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采用基于密度泛函理论的平面波赝势方法对SnO2:F体系的电子结构进行了第一性原理模拟计算.用广义梯度近似方法优化SnO2:F体系的晶胞结构,计算了体系基态总能.通过确定F掺杂对O的优先替代位置,计算了SnO2:F的能带结构、态密度、分波态密度.分析了F掺杂对SnO2晶体的电子结构和晶体性质及光学吸收边的影响,从理论上得出光学吸收边发生蓝移.对不同掺杂量的体系电子结构进行了分析.
关键词:
F掺杂
2')" href="#">SnO2
电子结构
态密度 相似文献
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采用基于第一性原理的密度泛函理论赝势平面波方法,对LiGaX2(X=S, Se, Te)的能带结构、态密度、光学以及弹性性质进行了理论计算. 能带结构计算表明LiGaS2 的禁带宽度为4.146 eV, LiGaSe2 的禁带宽度为3.301 eV, LiGaTe2 的禁带宽度为2.306 eV; 其价带主要由Ga-4p 层电子和X- np 层电子的能态密度决定; 同时也对LiGaX<
关键词:
电子结构
光学性质
弹性性质
LGX 相似文献
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从能带结构和态密度分析了黄铜矿CuAlS2的电子结构.对比未掺杂CuAlS2,从晶体结构、电子结构、电荷密度分布讨论了Mg和Zn替位Al掺杂对CuAlS2的影响.结果表明:Mg和Zn掺杂CuAlS2都导致晶格常数增大,Mg掺杂晶胞体积增大更多;掺杂在价带顶引入受主态,形成p型电导;Mg掺杂比Zn掺杂的受主能级电离能略小;而Zn掺杂CuAlS2体系总能更低,晶格结构更稳定.
关键词:
2')" href="#">CuAlS2
p型掺杂
电子结构
能带结构 相似文献
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从第一性原理出发,计算了MgCNi3的电子能带结构.MgCNi3中C 2p与Ni 3d轨道杂化使穿梭费米面上的Ni 3d能带表现出平面性,费米面落在态密度范霍夫奇异(vHs)峰的右坡上.vHs峰上大的电子态密度和铁磁相变点附近的自旋涨落是决定MgCNi3超导电性的重要因素.研究了三种替代式掺杂对其超导电性和磁性的影响,发现电子掺杂使费米能级下滑到态密度较低的位置,导致体系转变为无超导电性的顺磁相;同构等价电子数的金属间化合物的轨道杂化,引起费米面上态密度的减少,降低了超导电性;而空穴掺杂使费米面向vHs峰值方向移动,虽然费米面上电子态密度增大可能提高超导电性,但增强了的Ni原子磁交换作用产生铁磁序,破坏了超导电性.
关键词:
电子结构
超导电性
磁性
掺杂 相似文献
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A. S. Pomel’nikova M. N. Shipko M. A. Stepovich 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2011,5(2):298-304
A mechanism of the transformation of crystal lattices of borides under liquid boronizing of steels has been investigated.
It has been shown that nonstoichiometric borides with an FeB or Fe2B structure were the structure-formation element of phases in the hardened layer. The origin of the high rate of the formation
of borides at the initial stage of chemical-thermal treatment at 800–1100°C has been elucidated. It has been established that
the transformation of the Fe2B-FeB lattices was due to the enrichment of the FeB lattice by the boron vacancies. 相似文献
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A. L. Ivanovskii 《Physics of the Solid State》2003,45(10):1829-1859
This paper presents an overview of the current state of the art in research into the electronic structure and properties of a new superconductor, namely, MgB2, and a large number of related compounds by computational methods of the band theory. Consideration is given to the specific features of the surface states of magnesium diboride, the electron and hole doping effects in this compound, and the concentration dependences of the band structure and the properties of Mg1?xMexB2 and MgB2?yXy solid solutions and a number of superstructures. The electronic properties of AlB2-like phases, boron, higher borides, a series of ternary layered boron-containing phases, and compounds with structures of the antiperovskite type (MgCNi3 and others) are discussed in terms of their superconducting characteristics. The results obtained in modeling nanotubes and fullerene-like nanoparticles based on MgB2 and related borides are analyzed. 相似文献
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本文使用准确的第一原理方法,对超导体YB6和LaB6进行了电子结构比较研究,为进一步的实验研究提供理论参考. 相似文献
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The phase transition in the perovskite (Pv) SrRuO3 under pressure has been studied by using first-principles calculations based on density functional theory. The post-perovskite (Ppv) phase transition of SrRuO3 will take place under hydrostatic pressure of about 40 GPa. The stability of Ppv- SrRuO3 is justified by the enthalpy calculations, and this phase transition accompanies volume disconnection and magnetic moment collapses. The crystallographic data and the electronic structure of Ppv- SrRuO3 are also predicted. The crystal structure of Ppv- SrRuO3 is similar to that of Ppv- CaRuO3. A non-magnetic ground state is found in Ppv- SrRuO3. The strong hybridization of Ru and O is evident in the electronic structures of both phases. We expect that these results will help further understanding of SrRuO3 under high pressure. 相似文献
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ABSTRACT In Ni-based superalloys, it is usually found that borides can strengthen the grain boundaries, thereby resulting in an increase in mechanical strength and high-temperature creep properties. Due to their importance and prevalence in Ni-based superalloys, this study employs first-principles methods to investigate the crystallographic structure, anisotropic elastic response, and electronic properties of the major borides, such as M2B, M5B3 and M3B2 (M: Cr, Mo, W), respectively, which is necessary for the assessment of complex mechanical responses of Ni-based superalloys. The results demonstrate that the studied borides are all thermodynamically and mechanically stable. Among the M x B y binary borides analysed, Cr x B y exhibits the largest shear modulus, Young’s modulus, and Vicker hardness values, and these properties increase with the increase of B contents. The studied borides display nearly isotropic elastic properties except for W5B3 and W3B2. The electronic structure analysis of M x B y shows that the strong hybridisation between M-d and B-p orbitals leads to these borides exhibiting higher theoretical hardness, and the overlapping peaks of M-d and B-p orbitals move to a lower energy area with the increase of B contents, which leads to the increase of shear and Young’s moduli of M x B y . Furthermore, for M3B2 borides, the Cr-B bonds and Cr–Cr bonds are much stronger than the W-B & Mo-B bonds, and W-W & Mo-Mo bonds, respectively, which leads to Cr x B y yielding the largest values of elastic moduli. 相似文献
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H. Nakamura N. Hayashi N. Nakai M. Machida 《Physica C: Superconductivity and its Applications》2009,469(15-20):1024-1026
We perform first-principle phonon calculations for three typical iron-based superconductors, i.e., LaFeAsO,BaFe2As2, and FeSe. Though those crystals have different structures, we find that the optical modes associated with Fe vibration have almost similar characters. Moreover, we examine the pressure effect on phonons in FeSe. By increasing the external pressure, the phonon mode frequency related to Fe vibration effectively rises up and the electronic density of states at Fermi level also increases. These results may correlate to the critical temperature enhancement under high pressure. 相似文献
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利用基于密度泛函理论平面波赝势法的第一性原理计算, 研究了过渡金属化合物OsB2和OsO2的金红石相、黄铁矿相与萤石相三种结构在高压下的状态方程和结构特性以及OsO2可能的高压相变.理论计算结果支持OsB2与OsO2的萤石相是潜在超低可压缩性的硬性材料.同时,也分析了它们的电子结构,力求理解大体变模量和高硬度的微观机制.结果表明,可以利用过渡金属高的价电子浓度,掺入硼、氧、碳、氮等轻的元素形成强的
关键词:
过渡金属化合物
密度泛函理论
低压缩性
高压 相似文献
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M. Zemzemi N. Elghoul K. Khirouni S. Alaya 《Journal of Experimental and Theoretical Physics》2014,118(2):235-241
Cuprous oxide is selected as a promising material for photovoltaic applications. Density functional theory is used to study the structural, electronic, and thermodynamic properties of cuprous oxide by using the local density approximation and generalized-gradient approximation. The effect of pressure on the structural and electronic properties of Cu2O is investigated. This study confirms and characterizes the existence of new phases. Hexagonal and tetragonal phases are not completely indentified. We focus on the phase transition of the cuprous oxide under hydrostatic pressure to tetragonal and hexagonal (CdI2) structures. Variation of enthalpy with pressure is used to calculate the pressure of the phase transition. 相似文献