Density functional theory study of neutral AlS_n(n=2-9) clusters

This paper investigates the geometrical structures and relative stabilities of neutral AlS n(n = 2-9) using the density functional theory.Structural optimisation and frequency analysis are performed at the B3LYP/6-311G(d) level.The ground state structures of the AlS n show that the sulfur atoms prefer not only to evenly distribute on both sides of the aluminum atom but also to form stable structures in AlS n clusters.The structures of pure S n are fundamentally changed due to the doping of the Al atom.The fragmentation energies and the second-order energy differences are calculated and discussed.Among neutral AlS n(n = 2-9) clusters,AlS 4 and AlS 6 are the most stable.     

AlB+n(n=2～10)团簇结构和红外振动光谱研究

用密度泛函理论的B3LYP方法在6-311G(d)水平上对AlB+n(n=2～10)团簇几何结构、稳定性、电子结构和成键特性进行了系统理论研究,得到了AlB+n(n=2～10)团簇的最稳定结构.结果表明,硼原子间容易聚集,铝原子处于整个硼原子集团的外围.与相应中性AlBn团簇相比,Al-B键作用变弱,使正价团簇(n=6...     

YbBi_2单晶的电磁特性研究

本文主要研究了 Yb Bi2 单晶的电阻温度特性、磁化强度和温度的关系以及 2 K时的磁化特性 .实验发现 Yb Bi2 单晶具有金属特征 ;在 1 .8K以上没有表现出超导电性 ;其净电阻率之比高达 3 80 ;Yb Bi2 单晶是一种顺磁质 ;电阻温度特性曲线和磁化强度与温度关系都表明 :Yb Bi2 单晶在 5 5 K左右发生了明显的相变 .     

第一性原理研究Eu/N共掺杂锐钛矿TiO2光催化剂的电子和光学性质

基于密度泛函理论的第一性原理平面波赝势方法, 运用Vasp方法计算了Eu, N掺杂及Eu/N共掺杂锐钛矿TiO₂的结构, 并分析了其电子及光学性质. 通过计算发现有一些Eu的4f态电子在Eu掺杂锐钛矿TiO₂的体系的费米能级附近出现杂质能级, 并且N掺杂会使得锐钛矿TiO₂的禁带宽度减小. 对于共掺杂体系而言, Eu/N共掺杂的协同效应能导致锐钛矿TiO₂的晶格畸变及禁带宽度减小. 与此同时, 计算得到的光吸收谱表明Eu/N混合掺杂锐钛矿TiO₂展现出了明显的光谱吸收边缘红移. 这些计算结果表明Eu/N共掺杂锐钛矿TiO₂具有优良的光催化活性. 关键词： 2')" href="#">TiO₂ 共掺杂 可见光催化剂 密度泛函理论     

Spectral properties of a ■-configuration atom driven by a pair of bichromatic fields

The absorption spectrum and the incoherent fluorescence spectrum of the lower transition in an ■-configuration threelevel atomic system driven by a pair of bichromatic fields is investigated. The transmission of the absorption profile from a multipeaked feature to a single-peak feature is identified. Adjusting the relative phase between the two driving fields, the splitting effects of the spectral peaks occur both in the fluorescence and the absorption spectra. Furthermore, phase modulating can dramatically lead to a great suppression of the amplitudes of the whole absorption spectrum. Physically, this effect is attributed to the phase-sensitive nature of the populations and coherence between the atomic states of the system.     

Theoretical prediction of ion conductivity in solid state HfO2

A theoretical prediction of ion conductivity for solid state HfO2 is carried out in analogy to ZrO2 based on the density functional calculation. Geometric and electronic structures of pure bulks exhibit similarity for the two materials. Negative formation enthalpy and negative vacancy formation energy are found for YSH (yttria-stabilized hafnia) and YSZ (yttria- stabilized zirconia), suggesting the stability of both materials. Low activation energies (below 0.7 eV) of diffusion are found in both materials, and YSH’s is a little higher than that of YSZ. In addition, for both HfO2 and ZrO2 , the supercells with native oxygen vacancies are also studied. The so-called defect states are observed in the supercells with neutral and +1 charge native vacancy but not in the +2 charge one. It can give an explanation to the relatively lower activation energies of yttria-doped oxides and +2 charge vacancy supercells. A brief discussion is presented to explain the different YSH ion conductivities in the experiment and obtained by us, and we attribute this to the different ion vibrations at different temperatures.     

YbBi2单晶的电磁特性研究

本文主要研究了YbBi₂单晶的电阻温度特性、磁化强度和温度的关系以及2K时的磁化特性.实验发现YbBi₂单晶具有金属特征;在1.8K以上没有表现出超导电性;其净电阻率之比高达380;YbBi₂单晶是一种顺磁质;电阻温度特性曲线和磁化强度与温度关系都表明:YbBi₂单晶在55K左右发生了明显的相变.     

First-principles study of the electronic and optical properties of the (Y, N)-codoped anatase TiO2 photocatalyst

First-principles plane-wave pseudopotential calculations are performed to study the geometrical structures, formation energies, and electronic and optical properties of Y-doped, N-doped, and (Y, N)-codoped TiO₂. The calculated results show that Y and N codoping leads to lattice distortion, easier separation of photogenerated electron-hole pairs and band gap narrowing. The optical absorption spectra indicate that an obvious red-shift occurs upon Y and N codoping, which enhances visible-light photocatalytic activity.     

First-principles study of the electronic and optical properties of the （Y,N）-codoped anatase TiO2 photocatalyst

First-principles plane-wave pseudopotential calculations are performed to study the geometrical structures,formation energies,and electronic and optical properties of Y-doped,N-doped,and(Y,N)-codoped TiO 2.The calculated results show that Y and N codoping leads to lattice distortion,easier separation of photogenerated electron-hole pairs and band gap narrowing.The optical absorption spectra indicate that an obvious red-shift occurs upon Y and N codoping,which enhances visible-light photocatalytic activity.     

BmN (m=1-8)团簇结构和稳定性的密度泛函理论研究

使用泛函密度理论的B3LYP 方法,在6-311G*水平上对BmN（m=1-8）团簇的几何结构、电子结构、振动频率等进行了研究。结果表明,以Bm团簇作为设计母体,考虑在不同位置上结合N原子可以较快找到BmN类团簇基态结构;团簇的最稳定结构是平面结构,N原子倾向于在B团簇外端与两个B原子成键。通过对基态结构的平均束缚能和能量二次差分的计算,得到m=2和5的BmN团簇较为稳定。