TiO_2-Ti_3C_2 Composites with Pt Decoration as Efficient Photocatalysts for Ethylene Oxidation under Near Infrared Light Irradiation

Efficient utilization of solar energy is highly desirable in the field of photocatalysis. However, the near-infrared part of the solar spectrum, which constitutes about 44% of sunlight, has rarely been used. Herein, we report that the TiO_2 coupled with MXene Ti_3C_2 nanosheets shows promising photoactivity for ethylene oxidation under near infrared light(NIR) irradiation. Moreover, the Pt nanoparticle decoration can dramatically improve the performance of TiO_2–Ti_3C_2 nanocomposites. Within 15 minutes irradiation of the NIR light, 444 ppm of C_2 H_4 is completely removed over 1 wt%Pt–TiO_2–Ti_3C_2 and the catalyst exhibits excellent stability. It is expected that our work could provide useful information for the design and synthesis of efficient and stable NIR active photocatalyst for the target applications.     

BaTi_2Bi_2O的电子结构与磁性（英文）

采用第一性原理计算,我们对BaTi2Bi2O材料的电子结构和磁性做了详细的研究.其非磁性态的计算结果显示,费米能级处的态密度主要来自d2 z,d x2-y2和dxy三个轨道的电子.费米面主要有三部分组成,并且将其沿着矢量q1=(π/a,0,0)和q2=(0,π/a,0)平移时,第三部分费米面(沿着X-R连线)与第一部分费米面(M-A连线)a嵌套明显,计算得出磁化系数χ0(q)值出现在在X点出现峰值,这一点与峰M点的FeAs基超导体不同.上述磁化率峰值可以诱导产生自旋密度波,这使得BaTi2Bi2O的磁性基态是能量基本简并的bi-collinear antiferromagnetism(AF3)与blocked checkerboard antiferromagnetism(AF4)磁性态.随着空穴掺杂,χ0(q)的峰值降低并且变得有些不对称,而电子掺杂则导致峰值变大.一般认为超导序和磁性序相互竞争,当自旋涨落被完全压制时,超导出现,这正好可以解释为什么超导只能出现在空穴掺杂型化合物而非电子掺杂型里.     

XAuBi (X=Eu, Ba)拓扑nodal chain半金属的第一性原理研究

由于在磁性材料体系中缺失时间反演对称性,导致nodal chain被破坏,所以nodal chain通常存在于非磁材料中。但是,磁性材料EuAuBi是与常规磁性材料不同。本工作以第一性原理计算为研究方法,预言了在不考虑自旋轨道相互作用时,磁性材料EuAuBi体系为新型拓扑nodal chain半金属;当考虑自旋轨道耦合时,EuAuBi会退化为外尔半金属。对于非磁材料BaAuBi来说,在不考虑自旋轨道相互作用时,它同样是一种拓扑nodal chain半金属;当考虑自旋轨道相互作用时,由于C3旋转对称性的存在,BaAuBi会退化为狄拉克半金属。在XAuBi (X=Eu, Ba)中发现nodal chain半金属,会促进对六角材料的拓扑性质研究以及开拓其新实际应用领域。     

BaTi2Bi2O的电子结构与磁性

采用第一性原理方法,对BaTi₂Bi₂O的电子结构和磁性进行计算.非磁性态的计算结果显示:费米能级处的态密度主要来自d_z²,d_x²-y²和d_xy三个轨道,同时费米面也主要有三部分组成,并且将其沿着矢量q₁=(π/a,0,0)和q₂=(0,π/a,0)平移时,第三部分费米面(沿着X-R连线)与第一部分费米面(M-A连线)嵌套明显,计算得出磁化系数χ₀(q)在X点出现峰值,与峰值出现在M点的FeAs基超导体不同.上述磁化率峰值可以诱导产生自旋密度波,使得BaTi₂Bi₂O材料的磁性基态是bi-collinear antiferromagnetism(AF3)与blocked checkerboard antiferromagnetism(AF4)的二度简并态.随着空穴掺杂,χ₀(q)的峰值降低,而电子掺杂则导致峰值变大.当自旋涨落被完全压制时,超导出现,这可以解释为什么超导只出现在空穴掺杂型化合物而非电子掺杂型.     

Electron-correlation-induced band renormalization and Mott transition in Ca1-xSrxVO3

We present the local density approximate+Gutzwiller results for the electronic structure of Ca_1-xSr_xVO₃. The substitution of Sr²⁺ by Ca²⁺ reduces the bandwidth, as the V—O—V bond angle decreases from 180° for SrVO₃ to about 160° for CaVO₃. However, we find that the bandwidth decrease induced by the V—O—V bond angle decrease is smaller as compared to that induced by electron correlation. In correlated electron systems, such as Ca_1-xSr_xVO₃, the correlation effect of 3d electrons plays a leading role in determining the bandwidth. The electron correlation effect and crystal field splitting collaboratively determine whether the compounds will be in a metal state or in a Mott-insulator phase.     

潜在超导母体材料LaOMnSe的第一性原理研究

通过第一性原理计算,我们研究了LaOMnSe的结构、电子性质和磁性质．我们发现LaOMnSe在11点附近存在三个类空穴费米面,在M点附近有两个类电子费米面．如果将类空穴费米面平移（π,π,O）,则类空穴费米面就会和类电子费米面在很大程度上重叠,这种费米面嵌套将会导致磁不稳定性和自旋密度波（SI）、V）,和LaOFeAs...     

不同压强下BiI3的电子结构和光学性质

基于密度泛函理论研究了压强对BiI3的结构、电子和光学性质的影响,研究过程中考虑了自选轨道耦合（SOC）效应。计算的能带结果表明：在0GPa条件下,BiI3具有1.867电子伏特的间接带隙,随压强的提升带隙值降低;施加压强也能增强BiI3的光吸收系数和光电导率。0GPa条件下,BiI3的吸收系数为4×105 cm-1,光电导率为3×103 Ω-1•cm-1,因此 BiI3可作为光伏应用的备选材料。     

Fabrication of WO_3/TiO_2 Heterostructures for Efficiently Photocatalytic Gaseous Hydrocarbons Degradation: Origin of Photoactivity and Revisit the Role of WO_3 Decoration

Efficient oxidation of gaseous small molecular hydrocarbons under mild conditions remains a significant but challenging task to date.Here we report that WO_3 decoration can obviously improve the performance of Ti O_2(P25)toward the photocatalytic oxidation of several small molecular hydrocarbons(C_2H_6,C_3H_8 and C_2H_4)under simulated solar light irradiation.Among the WO_3/Ti O_2 heterostructures,the 10wt%WO_3/Ti O_2 nanocomposite shows the best photoactivities,which can efficiently oxidize C_2H_6,C_3H_8 and C_2H_4 within 15,9 and 8 minutes,respectively under simulated sunlight with a light intensity of 200 m W/cm~2.By strong contrast,a decreased photoactivity of Ti O_2 by coupling with WO_3 is observed when investigating the performance of photocatalysts toward the degradation of methylene blue(MB)in liquid phase.The opposing effect of WO_3 decoration on the performance of Ti O_2 is thoroughly investigated,and it is found that the improved photoactivities for gaseous hydrocarbon degradation is ascribed to the enhanced oxygen adsorption,resulting from WO_3 decoration rather than efficient charge separation within the WO_3/Ti O_2 heterostructures.     

Cs2AgF4中Jahn-Teller畸变导致的铁磁态和轨道序

利用基于密度泛涵的平面波赝势方法,研究了Cs2AgF4中Jahn-Teller（JT）畸变导致的轨道有序,以及铁磁态存在的机制.通过比较各种磁性态的总能和原胞实空间的电荷分布,我们发现：因为在a-b平面内Ag-F键长存在长短不同的交替变换,所以Ag的4d电子会交替占据dz2-x2和dz2-y2轨道.这种相互正交的轨道有...