Crystal chemistry and structural design of iron-based superconductors

The second class of high-temperature superconductors （HTSCs）, iron-based pnictides and chalcogenides, necessarily contain Fe2X2 （＂X＂ refers to a pnictogen or a chalcogen element） layers, just like the first class of HTSCs which possess the essential CuO2 sheets. So far, dozens of iron-based HTSCs, classified into nine groups, have been discovered. In this article, the crystal-chemistry aspects of the known iron-based superconductors are reviewed and summarized by employing ＂hard and soft acids and bases （HSAB）＂ concept. Based on these understandings, we propose an alternative route to exploring new iron-based superconductors via rational structural design.     

一种新的自由空间光通信调制方式——圆偏振位移键控

自由空间光通信(FSO)在开放的大气链路中传输光信号, 不可避免地会受到大气扰动和背景光噪声的影响, 导致系统的可靠性降低。为了抑制大气扰动等对FSO系统造成的不利影响, 提出一种新的光信号调制方式——圆偏振位移键控(CPOLSK)。该调制方式利用圆偏振光的两种旋光状态进行数据的传送, 接收端结合差分方法进行光信号接收。给出了CPOLSK的装置模型, 并对其性能进行了分析。与目前广泛采用的开关键控(OOK)、脉冲位置调制(PPM)方式相比, CPOLSK很好地抑制了背景光噪声的影响, 同时对光电探测器内部噪声也有一定的抑制效果。     

硒化前后电沉积贫铜和富铜的Cu(In1-xGax)Se2薄膜成分及结构的比较

采用电沉积法获得了接近化学计量比的贫铜和富铜的Cu（In_1-xGa_x）Se₂（CIGS）预置层,研究比较了两种预置层及其硒化处理后的成分和结构特性.得到了明确的实验证据证明,硒化后富铜薄膜中的Cu_xSe相会聚集凝结成结晶颗粒分散在表面.研究表明：在固态源硒化处理后,薄膜成分基本不变;当预置层中原子比Cu/（In+Ga）<11时,硒化后薄膜表面存在大量的裂纹;而当Cu/（In+Ga） >12时,可以消除裂纹的产生,形成等轴状小晶粒;富铜预置层硒化时蒸发沉积少量In,Ga和Se后,电池效率已达到68%;而贫铜预置层硒化后直接制备的电池效率大于2%,值得进一步深入研究. 关键词： 1-xGa_x）Se₂薄膜')" href="#">Cu（In_1-xGa_x）Se₂薄膜 电沉积 硒化处理 贫铜或富铜薄膜     

GaPO4晶体弹性与压电性能的研究

本文首先绘制了GaPO4晶体在（100）,（010）,（001）三个主晶面内慢度分布曲线,计算了声速的最大值,并与水晶进行了比较,发现GaPO4晶体的声速普遍小于水晶的声速;其次还探讨了GaPo4晶体压电系数d11及机电耦合系数k11随空间方向变化的规律,得到了GaPO4晶体d11,k11的最大值及其方向,并分别和水晶进行了比较,发现GaPO4晶体的d11和k11都远大于水晶的。这些结果将对GaPO4晶体在压电器件和声光器件的设计,开发及利用等方面具有一定的理论指导作用。     

醇及脱氧核糖与水分子间三体作用强度的快速准确计算

快速准确预测醇及脱氧核糖分子与水形成的氢键复合物的三体作用强度, 对准确模拟水环境下蛋白质和DNA的结构和功能至关重要. 基于对多体极化作用的理解, 在可极化偶极-偶极作用模型(PBFF)基础上, 将体系中的极性化学键视为化学键偶极, 通过模拟键偶极的极化计算了醇及脱氧核糖与水分子形成的氢键复合物的三体作用能. 通过拟合甲醇与水氢键复合物的三体作用能随分子间距离变化的能量曲线确定了所需的参数. 将模型和所确定的参数应用于计算更多的甲醇、 乙醇及脱氧核糖与水氢键复合物的三体作用能, 检验了模型的准确性和参数的可转移性. 计算结果表明, 可极化偶极-偶极作用模型及所确定的参数能够较好地预测具有不同结构的氢键复合物的三体作用强度, 其精度可与MP2方法的计算精度相当.     

Nonlinear Shift of the Raman A1 Mode in Ga-Incorporated CuInSe2 Thin Films

Composition dependence of quaternary CuIn1-x GaxSe2 films on Ga content has been systematically investigated by Raman scattering. The dominant A1 mode shifts from 174cm^-1 for CuInSe2 to 185cm^-1 for CuGaSe2 in an approximately polynomial curve other than a linear curve, indicating existence of asymmetric distribution of Ga and In on a microscopic scale in films. With Ga content x 〉 0.3, the significantly broadening and intensity decrease of A1 modes suggest the degradation of crystalline quality of chalcopyrite phase. Additionally, the quenching of additional Raman band at 183cm^-1 for the Ga-rich films reveals that CuAu-ordered phase can coexist in nominal chalcopyrite CuInSe2 films but not in CuGaSe2, due to Ga inhibition effect.     

The effect of composition on structural and electronic properties in polycrystalline CuGaSe2 thin film

Polycrystalline CuGaSe2 thin films on Mo-coated soda-lime glass substrates have been synthesized by coevaporation process from Cu, Ga and Se sources. Structural and electrical properties of the as-grown CuGaSe2 films strongly depend on the film composition. Stoichiometric CuGaSe2 is fabricated, as indicated by x-ray diffraction spectroscope （XRD） and x-ray fluorescence （XRF）. A two-phase region is composed of CuGaSe2 and Cu2-xSe phases for Cu-rich films, and CuGaSe2 and CuGa3Se5 phases for Ga-rich films, respectively. Morphological properties are detected by scanning electron microscope （SEM） for various compositional films, the grain sizes of the CuGaSe2films decrease with the extent of deviation from stoichiometric composition. Raman spectroscopy of Cu-rich samples shows that there exist large Cu-Se particles on the film surface. The results from Hall effect measurements for typical samples indicate that CuGaSe2 films are always of p-type semiconductor from Cu-rich to Ga-rich. Stoichiometric CuGaSe2 films exhibit relatively large mobility than any other compositional films. Finally, polycrystalline CuGaSe2 thin film solar cell with a best conversion efficiency of 6.02% has been achieved under the standard air mass （AM）1.5 spectrum for 100mW/cm^2 at room temperature （aperture area, 0.24cm^2）. The open circuit voltage of the CuGaSe2 solar cells is close to770 mV.     

铁超氧化物歧化酶活性中心结构研究

对氧化型、还原型及非活性形式铁超氧化物歧化酶Fe-SOD活性中心进行了量子化学计算和比较。在HF方法及LANL2DZ基组水平上获得了分子轨道能量、电荷分布以及原子轨道对前沿分子轨道贡献的信息。结果表明, Fe-SOD酶的活性形式的活性中心易于接受超氧自由基(O2- )的进攻而完成其生理功能。     

利用IEO方法求解多原子分子的振动能谱

对于线性多原子分子体系模型,借助从海森伯方程出发的不变本征算符(IEO)方法,很方便地求解了相应哈密顿量的本征能谱与振动频率,从而给出IEO方法在分子物理中的进一步应用.