Effects of charge on the structures and spin moments of Nil3 cluster

The structural stability and magnetic properties of the icosahedral Ni13, Ni13^＋1 and Ni13^-1 clusters have been obtained by utilizing all-electron density functional theory with the generalized gradient approximations for the exchange-correlation energy. The calculated results show that the ground states of neutral and charged clusters all favour a D3d structure, a distorted icosahedron, due to the Jahn-Teller effect. The radial distortions caused by doping one electron and by doping one hole are opposite to each other. Doping one electron will result in a 1/2 decrease and doping one hole will result in a 1/2 increase of the total spin. Both increasing interatomic spacing and decreasing coordination will lead to an enhancement of the spin magnetic moments for Nil3 clusters.     

Theoretical analysis of the radiation effect on the transient behavior of optoelectronic integrated devices

Theoretical analysis of the radiation effect on transient behavior of an optoelectronic integrated device composed of a heterojunction phototransistor and a light emitting diode is studied theoretically. First, the transient behavior and the rise time of this device before radiation are investigated based on the frequency response of the constituent devices and the optical feedback inside the device. Second, the effect of neutron irradiation flux on the transient behavior of this device is theoretically studied. The results show that, by increasing the optical feedback inside the device, the rise time in the amplification mode is increased along with an increasing output, while that in the switching mode can be reduced effectively, and the neutron irradiation reduces the transient response and the rise time in both the amplification and switching modes. This type of model can be exploited as optical amplifier, optical switching device, and other applications.     

Blended polyethylene terephthalate and polyethylene naphthalate polymers for scintillation base substrates

Polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are both good candidates for use as scintillation base substrates. One advantage is their relatively high density of 1.33 g cm⁻³. To enhance their relative strengths and to mitigate their weaknesses, we blended PET and PEN 1:1 by weight and found that the overall characteristics are improved. The wavelength at maximum emission was 415 nm, the refractive index was 1.61, and the light yield was 0.85 times that of PEN. These results increase the available options for base materials to be used as scintillators.     

含氧空位的氟掺杂二氧化锰助力稳定锌离子电池

将无机盐NH₄F加入到MnO₂的前驱体溶液中,通过高效、简单的一步水热法制备了具有氧缺陷的F掺杂α-MnO₂纳米棒(记为F-MnO₂)。氧空位和F掺杂对提高F-MnO₂的导电性、促进离子扩散、提高倍率性能起着至关重要的作用。另外,由于F掺杂,形成了F—Mn键,这可以有效地抑制放电产物中Mn³⁺的Jahn-Teller畸变,从而提高结构的稳定性。得益于这些协同效应,组装的Zn||F-MnO₂全电池在0.5 A·g^-1下,首圈放电比容量高达274 mAh·g^-1,且具有较长的循环寿命和优异的倍率性能。同时,通过循环伏安(CV)和恒流充放电(GCD)曲线证明了F-MnO₂的储能机制为H⁺和Zn²⁺的共嵌入/脱出过程。     

The electronic transport properties for a single-wall ZnO nanotube with different coupling interfaces

The transport properties of a single-wall ZnO nanotube contacted with two Au (Al or Cu ) electrodes are investigated by a theoretical approach. Our results suggest the contact resistance for ZnO nanotube connected with Au electrodes is the largest one as compared with Al and Cu acting as electrodes. The local density of states (LDOS) near the ZnO nanotube/Cu(Al) interface shows the strong electronic interaction. Also shown is that for Au–ZnO system, we can observe a best rectifying performance, the next is the Al–ZnO system, and the third is Cu–ZnO system. This rectification is also fully rationalized by the calculated transmission spectra, the spatial distribution of the lowest unoccupied molecular orbital and highest occupied molecular orbital states, and the electrostatic potential distribution.     

硅基超晶格Si1-xSnx/Si的能带结构

由于Si基发光材料能与现有的Si微电子工艺兼容,其应用前景被广泛看好. 设计具有直接带隙的Si基材料,备受实验和理论研究者的关注. 本文根据芯态效应、电负性差效应和对称性效应设计了Si基超晶格Si_1－xSn_x/Si. 其中Si_0.875Sn_0.125/Si为直接带隙材料. 在密度泛函框架内,采用平面波赝势法计算表明,Si_0.875Sn_{0.125相似文献}   

双原子分子激发态势能的自旋相关局域Hartree-Fock密度泛函理论方法

基于自旋相关局域Hartree-Fock (SLHF)势函数,本文提出了一种计算双原子分子激发态势能的密度泛函理论(DFT)方法,并将该方法应用于和的激发态势能曲线的计算。在只考虑交换能的情况下,本文的DFT计算结果与文献中精确方法和Hartree-Fock (HF)方法的结果符合的非常好,说明采用SLHF势函数作为交换势的DFT方法是一个很好的计算激发态势能的方法。本文还计算和探讨了电子的关联势函数和关联能,发现传统的近似方法在较大核间距的情况下大大低估了电子的关联能.     

宽绝对禁带的一维磁性光子晶体结构

提出了一种具有宽绝对禁带的一维磁性光子晶体结构,该结构由相同的折射率和物理厚度以及不同的波阻抗的两种磁性材料交替组合而成.通过传输矩阵法分析可得,相比于非磁性光子晶体,该光子晶体的禁带对入射角和偏振都不敏感,从而具有更宽的绝对禁带.合适地调节两种磁性材料的参数,增加两者波阻抗的差值,该光子晶体的绝对禁带宽度也相应地增加;调节两种磁性材料的物理厚度,其绝对禁带中心也会随之调整;最后,将两个满足上述条件的一维磁性光子晶体组成异质结构,其第一禁带宽度与禁带中心之间的比值可达到1.41以上.     

Theoretical studies on the structural, electronic, and optical properties of Ag2HgSnSe4

We investigate the electronic structure of Ag₂HgSnSe₄ in a wurtzite-stannite structure with the first principles method. This crystal is a direct band-gap compound. In addition the dielectric function, absorption coefficient, reflectivity, and energy-loss function are studied using the density functional theory in the generalized gradient approximation. We discuss the optical transitions between the valence bands and the conduction bands in the spectrum of the imaginary part of the dielectric function at length. We also find a very high absorption coefficient and a wide absorption band for this material. The prominent structures in the spectra of reflectivity and the energy-loss function are discussed in detail.     

用于乙烯环氧化反应的CuCs掺杂银基催化剂设计

最近的理论研究筛选出CuCs掺杂Ag基催化剂是一种高效的乙烯环氧化催化剂[ACS Catal. 11,3371 (2021)]. 然而,该工作是基于研究表面建模预测Ag基催化剂的性能,在实际反应过程中,Ag基催化剂是颗粒状的. 本文结合密度函数理论、Wulff构造理论和微观动力学分析来研究Ag基催化剂在颗粒模型上的催化性能. 研究表明,CuCs掺杂Ag基催化剂在选择性和活性方面都优于纯Ag基催化剂,这一点通过实验得到了证明. 进一步地表征分析发现,CuCs掺杂能促进颗粒的生长以及颗粒的分散,从而形成富含晶界的Ag颗粒. 此外,CuCs促进了催化剂表面亲电氧的形成,这均有利于环氧乙烷的形成和解吸. 本工作为理论与实验相结合的催化剂设计提供了一个案例研究.