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为模拟Nb含量对FeSiBCuNb系铁基纳米晶合金结构和磁学性能的影响,采用Amorphous模块构建了Fe88-xSi9B2CuNbx(x=1,3,5,7)的硬球密剁模型,通过分子动力学方法进行弛豫,淬火以及退火处理,得到了Fe88-xSi9B2CuNbx(x=1,3,5,7)铁基纳米晶合金结构.基于第一性原理的计算方法,分析了不同Nb含量的铁基纳米晶合金的晶体结构和磁学性能.结果表明:随着Nb含量的增加,体系的晶格常数和体积都有所增大,导电性减小,磁矩不断减小,并且Fe的3d轨道是体系磁矩的主要贡献者,Nb元素对体系非晶化的形成有一定的作用. 相似文献
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采用基于密度泛函理论的第一性原理分析方法的CASTEP软件,计算了W-Cux(x=6.25,12.5,18.75,25,31.25,37.5,43.75,50)合金的晶格参数、体模量、剪切模量、杨氏模量等力学常数,还计算了焓变值、能带结构、电子态密度和电荷布局,研究Cu不同含量对W-Cu合金力学性能的影响.结果表明:Cu的添加会增加W基体触头材料的可塑性,韧性大小随着Cu含量的升高而增加,在掺杂比例为43.75%时达到最大值,韧性增加使得产生微裂纹的概率减小;另外还计算了W-Cu合金的态密度、能带结构和电荷布局,结果表明随着Cu含量的增加,共价性降低,金属性增强,便于加工成型. 相似文献
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With the help of broadband dielectric spectroscopy in a wide temperature and frequency range, the conductivity spectra of ZnO polycrystalline ceramics are measured and the direct-current-like (DC-like) conductivity and relaxation polarization conductivity are observed successively along the frequency axis. According to the classical Debye theory and Cole-Cole equation, the physical meanings of the two conductivities are discussed. It is found that the DC-like conductivity corresponds to electron transportation over the Schottky barrier at the grainboundary. The relaxation polarization conductivity corresponds to electronic trap relaxation of intrinsic point defects (zinc interstitial and oxygen vacancy). When in the high frequency region, the relaxation conductivity obeys the universal law with the index n equal to the index α in the Cole-Cole equation as an indictor of disorder degree. 相似文献
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本文研究外加电场对离子交联聚乙烯的微观结构和能量特性的影响,使用分子模拟法建立PbO作硫化剂的交联聚乙烯分子模型,通过半经验法对模型进行几何优化同时施加沿X轴方向的外电场,计算离子交联聚乙烯的分子总能量、偶极矩、极化率、分子轨道能量、能隙、红外光谱、电荷分布并进行分析.得出结论:随着外加电场的上升,交联聚乙烯分子结构会发生变化,当外加电场过大时本文所建交联聚乙烯分子离子盐桥的S-Pb-S键将会发生断裂形成自由基.外加电场会使分子内部的电荷从交联聚乙烯碳链端部向离子盐桥转移,盐桥处Pb原子电荷量不断积累,到达临界点时将会断裂形成电荷量较大的Pb自由基,在外加电场的作用下进一步影响交联聚乙烯分子的稳定性导致其性能下降,研究结果对交联聚乙烯的电树枝老化生成提供参考. 相似文献
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基于密度泛函理论(DFT)的第一性原理计算方法,对本征Mn4Si7以及Ge, Al单掺杂和共掺杂Mn4Si7的晶体结构,能带结构,态密度以及光学性质进行了计算和分析.计算结果表明:本征态Mn4Si7的禁带宽度为0.810 eV,为直接带隙半导体材料,掺杂后晶体结构稍微变化,禁带宽度减小,且共掺杂时禁带宽度最小,电导率最好.Al以及Ge, Al共同掺杂时会产生杂质能级.掺杂后光子能量向低能级方向移动,光电导率,光吸收,反射系数都有所增大,说明掺杂改善了Mn4Si7的光学性质,从而可以提高光伏发电效率. 相似文献
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采用基于密度泛函理论的第一性原理分析方法的CASTEP软件,计算了Ni、C单掺杂和共掺杂SnO2的晶格参数、能带结构、电子态密度和布局,结果表明:单掺杂和共掺杂均使得晶胞体积略微增大,禁带减小,且仍属于直接带隙半导体,在价带顶和导带底产生杂质能级,其中Ni-C共掺杂时禁带最小,杂质能级最多,电子跃迁需要的能量更小,导电性也就最好.共掺杂时费米能级附近的峰值有所减小,局域性降低,原子间的成键结合力更强,使得SnO2材料也更加稳定. 相似文献
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基于密度泛函理论(DFT)的第一性原理计算方法,对本征Mn4Si7以及Ge,Al单掺杂和共掺杂Mn4Si7的晶体结构,能带结构,态密度以及光学性质进行了计算和分析.计算结果表明:本征态Mn4Si7的禁带宽度为0.810 eV,为直接带隙半导体材料,掺杂后晶体结构稍微变化,禁带宽度减小,且共掺杂时禁带宽度最小,电导率最好.Al以及Ge,Al共同掺杂时会产生杂质能级.掺杂后光子能量向低能级方向移动,光电导率,光吸收,反射系数都有所增大,说明掺杂改善了Mn4Si7的光学性质,从而可以提高光伏发电效率. 相似文献
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This paper investigates the electronic relaxation of deep bulk trap and interface state in ZnO ceramics based on dielectric spectra measured in a wide range of temperature, frequency and bias, in addition to the steady state response. It discusses the nature of net current flowing over the barrier affected by interface state, and then obtains temperature-dependent barrier height by approximate calculation from steady I--V (current--voltage) characteristics. Additional conductance and capacitance arising from deep bulk trap relaxation are calculated based on the displacement of the cross point between deep bulk trap and Fermi level under small AC signal. From the resonances due to deep bulk trap relaxation on dielectric spectra, the activation energies are obtained as 0.22 eV and 0.35 eV, which are consistent with the electronic levels of the main defect interstitial Zn and vacancy oxygen in the depletion layer. Under moderate bias, another resonance due to interface relaxation is shown on the dielectric spectra. The DC-like conductance is also observed in high temperature region on dielectric spectra, and the activation energy is much smaller than the barrier height in steady state condition, which is attributed to the displacement current coming from the shallow bulk trap relaxation or other factors. 相似文献
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