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从第一性原理出发,在局域密度近似下,采用基于密度泛函理论的平面波超软赝势计算方法系统地研究了高压对BaHfO3电子结构与光学性质的影响.能带结构分析表明;无压强和施加正压强作用时,BaHfO3为直接带隙绝缘体,而施加负压强时,BaHfO3则转变为间接带隙半导体;BaHfO3的带隙随压强增加而减小,且具有明显的非线性关系.对光学性质的分析发现:施加正压强后,光学吸收带边产生蓝移;负压强作用时介电函数虚部尖峰减少,光学吸收带边产生红移;施加压强后BaHfO3的静态介电常数和静态折射率均增大.上述研究表明施加高压有效调制了BaHfO3的电子结构和光学性质,计算结果为BaHfO3光电材料的设计与应用提供了理论依据. 相似文献
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在全电子水平上,采用广义梯度近似密度泛函理论和全势能线性缀加平面波方法并结合二维立方拟合方法,对LaNi3.75Al1.25合金的晶体结构与弹性性质进行了理论研究.计算结果给出合金的晶格常数a=b=0.5137 nm,c=0.4018 nm,Al原子在晶胞中的微观分布为同时占据部分3g和2c等价格位,弹性常数C11+C12=281.2,C13=82.3,C33=227.3,以及体弹性模量B=124.5、切变模量G=68.2 GPa.还对态密度、能带结构和电荷密度进行了计算分析,并给出材料LaNi3.75Al1.25的电子线性比热系数23.45 mJ/molK2.
关键词:
3.75Al1.25')" href="#">LaNi3.75Al1.25
储氢合金
全势能线性缀加平面波
弹性常数 相似文献
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基于第一性原理方法,探索M-Al-N(M=Ti,Zr,Hf)结构的稳定性,计算其力学性质.计算M-Al-N化合物的能量,发现除实验已知的结构Ti2AlN和Ti4AlN3、Zr2AlN、Hf2AlN外,还存在两种新的热力学稳定结构Zr4AlN3、Hf4AlN3.弹性常数和声子谱的计算,表明这两个结构是力学稳定和晶格动力学稳定的.计算M2AlN和M4AlN3的力学性质,发现它们具有高的体模量、剪切模量、弹性模量、维氏硬度等;分析其力学性质随组分比例、组成元素的变化规律,为该类材料的选择和应用提供理论依据.最后计算M2AlN和M4AlN3的电子态密度和分态密度、电子密度分布、Mulliken群分析等. 相似文献
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采用平面波赝势密度泛函理论方法计算了PtN2的坐标、平衡态的晶格常数、体弹模量、剪切模量和弹性常数,计算结果与已有的实验值和理论值符合较好.通过能量与体积曲线,可知STAA结构比黄铁矿结构具有更低的能量.根据计算结果和Pugh提出的经验判据,PtN2是易脆的硬物质,随着压强增加PtN2的脆性逐渐过渡到延性.两种结构的能带结构和态密度表明了黄铁矿结构的PtN2是半导体而STAA
关键词:
2')" href="#">PtN2
第一性原理
力学性质 相似文献
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运用第一性原理方法研究了L12型铝合金相Al3Sc和Al3Zr的晶体结构、电子结构和弹性.结合能和形成能的计算表明,两种合金具有较强的合金化能力,且Al3Zr较Al3Sc具有更强的结构稳定性.电子结构分析表明,费米能级以下较多的价电子数决定了Al3Zr具有较强的结构稳定性.计算并分析比较了两种合金相的单晶弹性常数(C11,C12和C44)以及多晶弹性模量(体弹性模量B、剪切模量G、杨氏模量Y、泊松比ν和各向异性因子A).通过对比实验和其他理论计算结果,进一步分析和解释了两种合金相的力学性质.
关键词:
铝合金
第一性原理
结构和电子性质
弹性 相似文献
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采用基于密度泛函理论的第一性原理平面波超软赝势方法,计算了Nb掺杂对TiO2/NiTi界面电子结构的影响.体系生成能的计算结果表明,4种TiO2/NiTi界面结构中,NiTi中Ti原子和TiO2中O原子相邻的界面,即Ti/O界面的生成能最大,结构最稳定.在Ti/O界面结构优化的基础上,态密度、电荷分布以及集居数的计算结果均表明:Nb原子取代界面上的Ti原子后,界面原子之间的结合力增强,且界面附近的基体和氧化层中原子之间的相互作用也增加,有利
关键词:
NiTi金属间化合物
2/NiTi界面')" href="#">TiO2/NiTi界面
电子结构
第一性原理计算 相似文献
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采用基于第一性原理的密度泛函理论全势线性缀加平面波法,使用广义梯度近似处理交换相关势能,首先计算了β-FeSi2的电子结构及其各元素各亚层电子的能态密度,β-FeSi2的电子能态密度主要由Fe的d层电子和Si的p层电子的能态密度确定;其次通过计算不同掺杂系统的总能量确定了掺杂原子在β-FeSi2中的置换位置,在β-FeSi2中,Co置换FeⅡ位置的Fe原子,Al置换SiⅠ位置的Si原子,这种择位置换与现有的计算结果完全一致;最后计算了Fe1-xCoxSi2和Fe(Si1-xAlx)2的电子结构,对它们的电子结构特征进行了分析,并探讨了电子结构对其热电性能(塞贝克系数、电传输及热传输性能)的影响.
关键词:
第一性原理
电子结构
热电性能
2')" href="#">FeSi2 相似文献
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Structural, elastic and mechanical properties of orthorhombic SrHfO3 under pressure have been investigated using the plane-wave ultrasoft pseudopotential technique based on the first-principles density functional theory. The calculated equilibrium lattice parameters and elastic constants of orthorhombic SrHfO3 at zero pressure are in good agreement with the available experimental and calculational values. The lattice parameters, total enthalpy, elastic constants and mechanical stability of orthorhombic SrHfO3 as a function of pressure were studied. With the increasing pressure, the lattice parameters and volume of orthorhombic SrHfO3 decrease whereas the total enthalpy increases. Orthorhombic SrHfO3 is mechanically stable with low pressure (<52.9 GPa) whereas that is mechanically instable with high pressure (>52.9 GPa). The bulk modulus, shear modulus, Young's modulus and mechanical anisotropy of orthorhombic SrHfO3 as a function of pressure were analyzed. It is found that orthorhombic SrHfO3 under pressure has larger bulk modulus, better ductility and less mechanical anisotropy than orthorhombic SrHfO3 at 0 GPa. 相似文献
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Zhenbao Feng Shouxin Cui Chenglin Bai Hengshuai Li 《Journal of Physics and Chemistry of Solids》2009,70(2):412-3461
Electronic structure and optical properties of SrHfO3 are calculated using the full potential linearized augmented plane wave plus local orbitals method. The calculated equilibrium lattice is in reasonable agreement with the experimental data. From the density of states (DOS) as well as charge density studies, we find that the bonding between Sr and HfO3 is mainly ionic and that HfO3 entities bond covalently. The complex dielectric functions are calculated, which are in good agreement with the available experimental results. The effect of the spin-orbit coupling on the optical properties is also investigated and found to be quite small. 相似文献
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First principles study of structural, elastic, electronic and optical properties of the cubic perovskite-type BaHfO3 has been reported using the pseudo-potential plane wave method within the local density approximation. The calculated equilibrium lattice is in a reasonable agreement with the available experimental data. The elastic constants and their pressure dependence are calculated using the static finite strain technique. A linear pressure dependence of the elastic stiffnesses is found. Band structures show that BaHfO3 is a direct band gap between the occupied O 2p and unoccupied Hf d states. The variation of the gap versus pressure is well fitted to a quadratic function. Furthermore, in order to understand the optical properties of BaHfO3, the dielectric function, absorption coefficient, optical reflectivity, refractive index, extinction coefficient, and electron energy loss are calculated for radiation up to 30 eV. We have found that O 2p states and Hf 5d states play a major role in the optical transitions as initial and final states, respectively. This is the first quantitative theoretical prediction of the elastic, electronic and optical properties of BaHfO3 compound, and it still awaits experimental confirmation. 相似文献
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Through first principles calculations, we investigated the electronic structure and lattice vibrational properties of BaHfO3. The optimized lattice constant of BaHfO3 is in agreement with experimental and theoretical results. Our results show that cubic BaHfO3 is an insulator with an indirect band gap of 3.5 eV. Besides, the calculation using the screened exchange local density approximation (sX-LDA) has been performed with the predicted minimum gap of 5.3 eV. The phonon dispersion curves of BaHfO3 were also calculated. All positive phonon frequencies in the Brillouin zone were found, indicating the stability of BaHfO3 structure. 相似文献
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Using first-principles density functional calculations, the effect of high pressures, up to 40 GPa, on the structural and elastic properties of ANCa3, with A = P, As, Sb, and Bi, were studied by means of the pseudo-potential plane-waves method. Calculations were performed within the local density approximation and the generalized gradient approximation for exchange-correlation effects. The lattice constants are in good agreement with the available results. The elastic constants and their pressure dependence are calculated using the static finite strain technique. We derived the bulk and shear moduli, Young's modulus, Poisson's ratio and Lamé's constants for ideal polycrystalline ANCa3 aggregates. By analysing the ratio between the bulk and shear moduli, we conclude that ANCa3 compounds are brittle in nature. We estimated the Debye temperature of ANCa3 from the average sound velocity. This is the first quantitative theoretical prediction of the elastic properties of PNCa3, AsNCa3, SbNCa3, and BiNCa3 compounds, and it still awaits experimental confirmation. 相似文献
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M.G. Brik 《Solid State Communications》2011,151(23):1733-1738
Detailed ab initio calculations of the structural, electronic, optical and elastic properties of CsCaBr3, CsGeBr3 and CsSnBr3 crystals are presented in this paper. Based on the obtained results, CsCaBr3 is characterized as a dielectric with an indirect band gap, whereas CsGeBr3 and CsSnBr3 are semiconductors with very narrow direct band gaps. The first theoretical estimations of the refractive indexes for all compounds are reported. Variations of the electron density difference distribution induced by changes of the second cation were analyzed and related to the type of chemical bonding between atoms. In addition, the complete set of elastic parameters (which includes the elastic constants, elastic compliance constants, bulk and Young’s moduli, elastic anisotropy) was obtained. Directional anisotropy of elastic properties was visualized; the directions in the crystal lattices, along which the maximal and minimal values of the Young’s moduli are realized, were identified. 相似文献
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在第一性原理框架下,采用赝势平面波方法研究了三种Mg2Si同质异相体的晶胞结构、电子结构和弹性性质随压强的变化关系.研究发现,反萤石结构Mg2Si、反氯铅矿结构Mg2Si和Ni2In型Mg2Si分别在压强为0-7 GPa,7.5-20.2 GPa和21.9-40 GPa范围内能够保持结构稳定.计算获得了不同压强下Mg2Si的弹性常数、体模量、剪切模量、杨氏模量、泊松比和各向异
关键词:
态密度
电子结构
弹性常数
第一性原理 相似文献
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First-principles study on the catalytic role of Ag in the oxygen adsorption of LaMnO3(0 0 1) surface
Yongjun ZhouZhe Lü Pengzhen GuoYanting Tian Xiqiang HuangWenhui Su 《Applied Surface Science》2012,258(7):2602-2606
In the present paper, the catalytic role of Ag in the oxygen adsorption of LaMnO3(0 0 1) surface has been theoretically investigated using first-principles calculations based on the density functional theory (DFT) and pseudopotential method. The O2 adsorption energy is larger for the vertical adsorption and the covalent bond was formed between O2 molecule and surface Mn. The calculation of electronic properties of interaction between Ag atom and LaMnO3(0 0 1) surface demonstrates that the most stable position for Ag adsorption is hollow site. The O2 adsorption energy dramatically increased from 0.298 eV to 1.108 eV due to Ag pre-adsorbed. It is Ag pre-adsorbed that facilitates O2 adsorption on surface. The bond length and bond population of O2 molecule indicate that Ag atom facilitates O2 molecule dissociative adsorption. The Ag atom strengthens LaMnO3(0 0 1) substrate activity and activity center was formed on surface, which enhances the electrocatalytic activity of LaMnO3 as solid oxide fuel cells cathode material at low temperature. 相似文献
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The equilibrium lattice constant, the cohesive energy and the electronic properties of light metal hydrides LiXH3 and XLiH3 (X = Be, B or C) with perovskite lattice structures have been investigated by using the pseudopotential plane-wave method. Large energy gap of LiBeH3 indicates that it is insulating, but other investigated hydrides are metallic. The pressure-induced metallization of LiBeH3 is found at about 120 GPa, which is attributed to the increase of Be-p electrons with pressure. The electronegativity of the p electrons of X atom is responsible for the metallicity of the investigated LiXH3 hydrides, but the electronegativity of the s electrons of X atom plays an important role in the metallicity of the investigated XLiH3 hydrides. In order to deeply understand the investigated hydrides, their optical properties have also been investigated. The optical absorption of either LiBeH3 or BeLiH3 has a strong peak at about 5 eV, showing that their optical responses are qualitatively similar. It is also found that the optical responses of other investigated hydrides are stronger than those of LiBeH3 and BeLiH3 in lower energy ranges, especially in the case of CLiH3. 相似文献
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Qi-Jun Liu Zheng-Tang LiuJi-Chao Chen Li-Ping FengHao Tian Wei Zeng 《Applied Surface Science》2012,258(8):3455-3461
Structural, electronic and chemical bonding properties of the (0 0 1) surface of cubic SrHfO3 have been investigated with both SrO and HfO2 termination using the plane-wave ultrasoft pseudopotential technique based on the first-principles density-functional theory. The relaxed structures of two slabs have been analyzed, which shows the interplanar distance of two slabs has the same changed trend. The electronic band structures and density of states of two slabs have been discussed, showing the reduced band gaps by comparison with those of bulk system. The chemical bonding between Sr and O between the surface layer and subsurface layer as well as Hf and O has been increased. The surface energy, work function and stability have been calculated, which indicates SrO-terminated slab is more stable. 相似文献