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11.
通过第一性原理赝势平面波方法研究了氧在Nb(110)表面的吸附性质随覆盖度变化规律. O在Nb(110)表面最稳定吸附位是洞位,次稳定吸附位是长桥位. 在长桥位吸附时, O诱导Nb(110)表面功函数随覆盖度的增加而几乎线性增加;但当O在洞位吸附时, 与干净Nb表面相比, 覆盖度为0.75 ML和1.0 ML时功函数增加, 而覆盖度为0.25 ML和0.5 ML时功函数减小.通过对面平均电荷密度分布和偶极矩变化的讨论, 解释了由吸附导致功函数复杂变化的原因.通过对表面原子结构和态密度分析, 讨论了O在Nb表面吸附时引起表面原子结构变化以及O和Nb(110)表面原子的相互作用. 相似文献
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应用第一性原理系统地研究了不同端面Si2CN4(010)模型的表面特性.通过3种可能表面模型解离能的比较,表明位于SiN层内的Si—NⅡ 键结合最强,而与碳二亚胺链状结构相连的Si—NⅠ 键结合最弱,因此易于形成以Si/NⅠ 键为端面的表面.文中还研究了弛豫前后表面的原子结构和电子特性,表面的NⅠ 原子容易形成新键,这是由于不饱和的NⅠ 原子在费米能级处有较高的态密度,电子结构不稳定,相反表面C原子状态较稳定,无明显的成键趋势.
关键词:
2CN4')" href="#">Si2CN4
表面
原子结构
电子结构 相似文献
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用基于密度泛函理论的第一性原理方法研究了Nb(110)表面氧原子覆盖度分别为0.25、0.50、0.75 和1.00单层时对氧分子解离的影响. 结果表明, 在氧原子覆盖度不大于0.50单层时, 由于氧分子和表面铌原子的较强相互作用, 使它们能够自发解离. 然而在氧原子覆盖度为0.75单层时, 氧分子只能够在未占据的洞位附近解离, 同时发生严重的晶格畸变. 在形成一个氧原子单层后(1.00 单层), 氧分子只能弱吸附在Nb(100)表面上,此时氧原子向内扩散成为氧分子继续解离的速率决定步骤. 这些结果从理论上解释了在形成一个氧原子单层后, Nb(110)表面氧分子吸收速率迅速下降的原因. 相似文献
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通过第一性原理赝势平面波方法研究了氢原子在B2-NiAl和Cr合金中的占位以及对键合性质的影响. H在NiAl的富Al和富Ni八面体间隙杂质形成能分别为-2.365和-2.022eV,而在四面体间隙不稳定. H在Cr的八面体和四面体间隙的杂质形成能分别为-2.344和-2.605eV. H在NiAl中的最稳定位置为富Al八面体间隙,而在Cr中的最稳定位置是四面体间隙. 可以预期H在B2-NiAl/Cr体系中主要占据Cr 的四面体间隙位置. 通过分析原子结构、电荷集居数、价电荷密度以及态密度,讨论了H对B2
关键词:
NiAl/Cr双相合金
H原子
第一性原理 相似文献
16.
Density functional theory analysis of electronic structure and optical properties of La-doped Cd_2SnO_4 transparent conducting oxide 下载免费PDF全文
The electronic structural, effective masses of carriers, and optical properties of pure and La-doped Cd_2SnO_4 are calculated by using the first-principles method based on the density functional theory. Using the GGA+U method, we show that Cd_2SnO_4 is a direct band-gap semiconductor with a band gap of 2.216 eV, the band gap decreases to 2.02 e V and the Fermi energy level moves to the conduction band after La doping. The density of states of Cd_2SnO_4 shows that the bottom of the conduction band is composed of Cd 5 s, Sn 5 s, and Sn 5 p orbits, the top of the valence band is composed of Cd 4d and O 2p, and the La 5 d orbital is hybridized with the O 2 p orbital, which plays a key role at the conduction band bottom after La doping. The effective masses at the conduction band bottom of pure and La-doped Cd_2SnO_4 are 0.18 m0 and 0.092 m_0, respectively, which indicates that the electrical conductivity of Cd_2SnO_4 after La doping is improved. The calculated optical properties show that the optical transmittance of La-doped Cd_2SnO_4 is 92%, the optical absorption edge is slightly blue shifted, and the optical band gap is increased to 3.263 eV. All the results indicate that the conductivity and optical transmittance of Cd_2SnO_4 can be improved by doping La. 相似文献
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Influence of Interface Structure of Co/Cu (100) Superlattices on Electronic Structure and Giant Magnetoresistance 下载免费PDF全文
Electronic structures and magnetoresistance (MR) of Co3 Cu5 and Co3 Cur models as well as their interface atom exchange models Co2 CuCoCu4 and Co2 CuCoCu6 are investigated by the tlrst-principles pseudopotential planewave method based on density functional theory. Charge transfer, magnetic moment, density of states, spin asymmetry factor, and MR ratio are discussed. The results show that the values of charge transfer and spin asymmetry factor at the Fermi level of Co layers are closely related to the neighbouring background of the Co layer. The Co layer with two sides adjacent to the Cu layer would transfer more charge to the Cu layer than other neighbouring background and have the largest spin asymmetry factor at the Fermi level. The Co layer with two neighbouring Co layers (interior Co) would gain a little charge and have the smallest spin asymmetry factor at the Fermi level. Two-current model is used to evaluate the MR ratio of Co2CuCoCu4 (Co2CuCoCu6) to be larger than that of Co3 Cu5 (Co3 CUT), which can be explained by the charge transfer and spin asymmetry factor. 相似文献
19.
本文采用第一性原理计算方法与准谐德拜模型相结合研究了C、N取代掺杂O原子对β-Ti3O5和λ-Ti3O5的电子结构以及相变温度的影响规律。结果表明:C元素对两相的电学特性影响较大,掺杂后β-Ti3O5和λ-Ti3O5的带隙宽度分别增加至1.25 eV和1.5 eV;氮元素的掺杂使β-Ti3O5的带隙增大到0.5 eV,同时仍然保持λ-Ti3O5的金属性不变,加剧了相变前后两相的电学差异,N掺杂使Ti3O5更适于应用在光学存储领域;同时对N掺杂Ti3O5的相变影响进行了研究,发现N掺杂可以有效降低相变温度。 相似文献
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磁致伸缩和磁晶各向异性来源于自旋轨道耦合及晶体场效应,两种效应作用效果将对Fe-Ga大磁致伸缩合金研究方向将起指导作用.通过基于均匀梯度近似的线形缀加平面波法研究了Fe-Ga磁致伸缩合金中D03、B2-like、L12结构在施加自旋轨道耦合效应前后Fe原子3d轨道劈裂情况,轨道电子数及磁晶各向异性.结果表明,自旋轨道耦合效应可以进一步劈裂D03及L12立方结构晶体场,D03和L12结构中Fe原子3d轨道电子数,尤其是dxy和d(x2-y2)轨道下自旋电子数由于自旋轨道耦合作用发生改变;但自旋轨道耦合对B2-like结构作用微弱.Fe-Ga磁致伸缩合金中磁晶各向异性主要由晶体场效应决定. 相似文献