钙钛矿型ScRh3X（X=B，C，N）的第一性原理研究

利用第一性原理研究了钙钛矿型的ScRh3X（X=B,C,N）及其固溶体的结构、弹性、电子性质等。研究结果表明,对于平衡状态下的ScRh3BxC1-x（0〈x〈1）固溶体,其结构参数和已知的实验数据相一致,和ScRh3C结构相比,在0〈x〈1的范围内,固溶体ScRh3BxC1-x的体积弹性模量和弹性常数C44随着价电子浓度的增加增大,而剪切模量却表现出单调下降的趋势。本文根据计算得到的电子结构信息对这些现象进行了分析,发现剪切模量比体积弹性模量或C44能更好的预测该体系的硬度。     

Defect formation and its effect on the thermodynamic properties of Pu2Zr2O7 pyrochlore: a first-principles study

In the past decades, pyrochlores, such as Gd₂Zr₂O₇, have demonstrated great potential to immobilize nuclear wastes such as Pu, which results in the production of Pu₂Zr₂O₇. Due to the high radioactivity of Pu, it is difficult to investigate the radiation response behavior of Pu₂Zr₂O₇ and its physical properties of the damaged state experimentally. Consequently, few related data have been reported in the literature thus far. In this study, first-principles calculations have been carried out to investigate the defect formation and its effect on the thermodynamic properties of Pu₂Zr₂O₇. It reveals that Pu_Zr antisite and O_8a interstitial defects are very easy to form in Pu₂Zr₂O₇. In particular, the O_8a interstitial defect can be formed spontaneously, while it is mechanically unstable. When vacancy, interstitial or antisite defects are formed in Pu₂Zr₂O₇, and the elastic moduli and Debye temperature are decreased. Besides, better ductility is resulted. As compared with other zirconate pyrochlores, such as Gd₂Zr₂O₇, the Pu₂Zr₂O₇ is suggested to be less resistant to radiation-induced amorphization. This study demonstrates that the created defects due to self-radiation from actinide decay have remarkable influences on the thermophysical properties of Pu₂Zr₂O₇.     

Theoretical study on composition-dependent properties of ZnO·nAl2O3 spinels. Part II: Mechanical and thermophysical

Knowledge on the mechanical and thermophysical properties of ZnO·nAl₂O₃ is essential for practical applications. Based on the first-principles calculations and the bond valence method, the disordered spinel-type structure of ZnO·nAl₂O₃ (n = 1–4) was constructed to investigate the composition-dependent mechanical and thermophysical properties. The effects of cation substitution on the hardness, elastic modulus, thermal expansion, and thermal conductivity were revealed from the insights into the chemical bonds. At a higher n, the tetrahedral bond is stronger, manifested as its higher hardness and bulk modulus as well as smaller thermal expansion coefficient. Meanwhile, the octahedral bond is weaker, leading to the lower hardness and bulk modulus, along with the larger expansion coefficient. In consequence, the hardness and elastic moduli of ZnO·nAl₂O₃ are improved moderately while the expansion coefficient is decreased with the rise of n. Due to the different vibration characteristics of Zn^IV and Al^IV, the cation disorder in the 8a site provides the primary source of phonon scattering, resulting in the dramatic reduction of thermal conductivity as n increases. The understanding offers guidance on the application-oriented design of new oxide spinels.     

InAs基范德华异质结界面电荷转移特性第一性原理计算的研究进展

由低维InAs材料和其他二维层状材料堆叠而成的垂直范德华异质结构在纳米电子、光电子和量子信息等新兴领域中应用广泛。探索跨结界面的电荷转移机制对于全面理解该类器件的非凡特性至关重要。第一性原理计算在揭示界面电荷转移特性与各种能量稳定型InAs基范德华异质结的电、光、磁等原理物理特性和器件性能变化之间的内在关系方面发挥着不可比拟的作用。文中梳理、总结和探讨了近年来InAs基范德华异质结间界面电荷转移特性的理论研究工作与潜在的功能应用,提出在理论方法和计算精度方面大力发展第一性原理计算的几个途径,为更好地开展InAs基范德华异质结的基础科学研究和应用器件设计提供可借鉴的量化研究基础。     

Ni掺杂CdS电子结构和光学性质的第一性原理计算

采用基于密度泛函理论框架下的第一性原理计算方法,对纤锌矿结构CdS和CdS∶Ni几何结构、能带结构、电子态密度和光学性质进行了系统的研究。计算结果表明,Ni原子掺入CdS后晶格常量均减小,晶格发生局部畸变;Ni的掺杂在费米面附近引入杂质能级,极大地提高了CdS系统的导电性。光学性质的计算结果显示,掺杂导致在可见光区域出现了强度微弱的新吸收峰。所有结果表明,Ni掺杂CdS体系是极具潜力的透明导电材料。     

Structure stability and configuration evolution of Al_n(n=3, 4, 6, 13, 19) clusters

As a special phase in the process of transformation from atoms or molecules to bulk materials, a cluster represents an original state of a condensed matter. For studies on structures and properties of clusters it is a basic problem to investigate how atoms or molecules form clusters and what changes will take place during the configuration evolu- tion of clusters. Recently Aln clusters attract many researchers’ attention because of its simple electronic structures and unique conductive charac…     

Li+嵌Al反应的热力学分析及实验研究

利用第一原理赝势平面波方法计算了Al-Li合金中3种平衡相AlLi、Al2Li3和Al4Li9的形成焓,得出AlLi相的形成焓最低,表明当Li 嵌入Al电极时,优先形成AlLi相。为了验证上述结论,将Al薄片与金属锂对电极组成扣式电池,对Al电极进行电化学性能测试和结构表征。实验结果与理论计算的结果相吻合,表明可以采用第一原理赝势平面波方法预测铝作锂离子电池负极时的电化学反应性能。     

First-principles Investigation of the Structural,Electronic and Elastic Properties of Al2Ca and Al4Sr Phases in Mg-Al-Ca（Sr） Alloy

First-principles calculations have been carried out to investigate the structural stabilities, electronic structures and elastic properties of Mg17Al12, Al2Ca and Al4Sr phases. The optimized structural parameters are in good agreement with the experimental and other theoretical values. The calculated formation enthalpies and cohesive energies show that Al2Ca has the strongest alloying ability, and Al4Sr has the highest structural stability. The densities of states （DOS）, Mulliken electronic populations, and electronic charge density difference are obtained to reveal the underlying mechanism of structural stability. The bulk modulus, shear modulus, Young＇s modulus, and Poisson＇s ratio are estimated from the calculated elastic constants. The mechanical properties of these phases are further analyzed and discussed. The Gibbs free energy and Debye temperature are also calculated and discussed.     

ATaO_3（A=K,Na）电子结构和光学性质的第一性原理研究

采用第一性原理广义梯度近似（GGA）下的全电势线性缀加平面波（FP-LAPW）方法计算出立方相ATaO3（A=K,Na）的电子能带结构、态密度,发现了其光学性质.通过对两种材料的对比分析发现,KTaO3和NaTaO3价带顶均出现在0.15089eV处,KTaO3的导带底在2.02849eV处,NaTaO3的导带底在2.27339eV处,NaTaO3比KTaO3的导带底高,因而禁带宽度较大;NaTaO3中Ta5d电子和O2p电子之间的轨道杂化比KTaO3中的轨道杂化弱,Na的粒子性较K更强,因此,NaTaO3的光催化活性明显大于KTaO3.     

Optical property of amorphous semiconductor mercury cadmium telluride from first-principles study

The structural and optical properties of amorphous semiconductor mercury cadmium telluride (a-MCT) are obtained by the first principles calculations. The total pair distribution functions and the density of states show that the a-MCT has the semiconductor characteristic. The calculated results of dielectric function show that E ₂ peak of the imaginary of dielectric function for the crystal mercury cadmium telluride abruptly disappears in the amorphous case due to the long-range disorders. And the imaginary of dielectric function of a-MCT shows a large broad peak, which is in agreement with the available results of other amorphous semiconductors. From the linear extrapolation of the curve ħωɛ ₂(ω)^1/2 versus ħω, it can be obtained that the optical energy gap of amorphous semiconductor Hg_0.5Cd_0.5Te is 0.51±0.05 eV. Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2007CB613205), the National Natural Science Foundation of China (Grant Nos.10725418, 10734090, 60576068), the Key Fund of Shanghai Science and Technology Foundation (Grant No. 08JC1421100) and the Knowledge Innovation Program of the Chinese Academy of Sciences