Effect of crystal field on the formation and diffusion of oxygen vacancy at anatase (101) surface and sub-surface

The intrinsic oxygen vacancy (O_v) in TiO₂ is a vital topic of semiconductor materials. Here, we use the first-principles calculations to explore the formation and diffusion properties of O_v at anatase (101) slab, combined with the crystal filed theory. The calculated result shows that O_v at subsurface is not only more stable than that at surface, but also prefers to cluster together at subsurface. The stability of O_v at subsurface is mainly attributed to the Ti3d orbitals in different crystal fields occupied by the excess electrons. Further calculation reveals that the O_v diffusion is greatly affected by the excess electrons. These results presented here show the importance of 3d orbitals in different crystal field, which should be helpful to understand the behavior of O_v at other transition metal oxide.     

Sn/Sn3O4?x heterostructure rich in oxygen vacancies with enhanced visible light photocatalytic oxidation performance

Sn3O4,a common two-dimensional semiconductor photocatalyst,can absorb visible light.However,owing to its rapid recombina-tion of photogenerated electron?hole pairs,its absorption is not sufficient for practical application.In this work,a Sn nanoparticle/Sn3O4?x nanosheetheterostructurewaspreparedbyin situreductionofSn3O4underaH2atmosphere.TheSchottkyjunctionsformedbetweenSnand Sn3O4?x can enhance the photogenerated carrier separation ability.During the hydrogenation process,a portion of the oxygen in the semicon-ductor can be extracted by hydrogen to form water,resulting in an increase in oxygen vacancies in the semiconductor.The heterostructure showed the ability to remove Rhodamine B.Cell cytocompatibility experiments proved that Sn/Sn3O4?x can significantly enhance cell compat-ibility and reduce harm to organisms.This work provides a new method for the fabrication of a Schottky junction composite photocatalyst rich in oxygen vacancies with enhanced photocatalytic performance.     

基于分子动力学模拟的含缺陷石墨烯力学性能的研究

基于分子动力学模拟的方法,研究了空位缺陷的位置、形状以及原子缺失率对石墨烯杨氏模量的影响。研究结果表明,单空位缺陷的位置对石墨烯杨氏模量有一定的影响,当施加应力方向与边缘缺陷的截面方向相同时,边缘缺陷比中间缺陷使得石墨烯的杨氏模量下降更少。研究结果还发现,映射横向长条状缺陷、映射纵向长条状缺陷、映射圆孔状缺陷和随机缺陷都使得石墨烯杨氏模量随着原子缺失率的增大而减小。对于映射圆孔状缺陷和随机缺陷,锯齿型石墨烯杨氏模量减小的幅度与扶手型的减小幅度相差不大。对于映射横向长条状缺陷和映射纵向长条状缺陷,锯齿型和扶手型石墨烯杨氏模量的减小幅度相差较大,这与石墨烯的手性矢量方向和条状缺陷方向是否一致有关。     

氧离子导体β-La2Mo2O9结构性质的第一性原理研究

采用第一性原理方法研究了β-La2Mo2O9结构性质.研究发现结构中Mo和周围的O形成MoO4或MoO5两种形式的多面体，La则形成LaO8和LaO7多面体.O(1)、O(2)、O(3)三种氧位置的占有率分别为100％、91.7％和25％，与实验相符.对Mo-O(1)键长分析表明，在MoO4和MoO5两种多面体中Mo-O(1)键长劈裂成两种键长形式.所有结构组态可通过P213空间群的相应操作而互相转换，显示结构具有P213空间群的对称性.模拟结果可能是β-La2Mo2O9结构在空间的局域或者本征极小结构.     

当代大学生"失信"现象之反思

大学生是国家的未来建设者和接班人,他们的诚信状况将直接关乎我国社会主义现代化建设的顺利进行。本文分析了当代大学生诚信缺失的原因,并从德育教育、社会的支持及建立诚信评估机制等方面提出治理的对策。     

BaTiO_3基抗还原陶瓷材料的研究

研究了 Ba Ti O3基抗还原陶瓷材料的结构和介电性质 ,讨论了 Zr O2 、Mn O和 BT系中摩尔比 m对瓷料抗还原性能和介电性能的影响 .通过调整上述参量并加入适量的添加剂 ,获得了在氮气中烧成并符合 F组性能要求的 Ba Ti O3基抗还原陶瓷材料     

碲镉汞退火过程的电子结构变化的理论模型

本文提出了退火过程中碲镉汞电子结构变化的理论模型,并根据此理论模型建立了理论公式.由理论公式经计算得出的理论曲线与实验曲线很好地吻合,从而证明了理论模型的正确性.     

Si晶体中60°位错与空位缺陷相互作用的分子动力学研究

为了研究晶格常数不匹配的异质结结构(Si1-xGex/Si)在生长过程中低温缓冲层内的位错运动特性,在Si晶体中建立了60°位错偶极子,以及相对于位错不同空间位置的5种六边形环状空位缺陷模型.基于分子动力学理论,并通过Parrinello-Rahman方法施加剪应力使位错运动,研究了不同空间位置空位缺陷对于60°位错运动的影响,发现各种类型的空位缺陷均会阻碍位错运动,导致位错线弯曲,而位错远离空位缺陷的部分在交会过程中出现了先加速、后减速的现象.模拟结果表明:使位错不被钉扎住的临界外加剪应力随着温度的上升而减小,在上述模型中当温度达到300K以上就稳定于0.6 GPa附近,小于SiGe体系中的失配应力,说明空位缺陷不会成为60°位错的钉扎点,仅会对其运动产生迟滞.     

《二十四诗品》中的道家天人合一思想

《二十四诗品》中的道家天人合一思想，首先表现在《雄浑》《冲淡》《疏野》等诸品对诗人人格修养的论述中。它们要求诗人在人格修养上效法道的无为、自然、虚、静的精神，从而与道冥合为一。其次，表现在《旷达》《绮丽》《纤秾》等诸多品目所描绘的诗歌境界中。它们表现的是人在大自然中与自然山水相亲相融，从而达到无为、自然、虚、静的人生境界，与道冥合为一。     

Blue TiO2 polymorph: An efficient material for dye-sensitized solar cells fabricated using a low-temperature sintering process

Recently,surface-disordered or non-stoichiometric TiO_2,such as blue TiO_2(B-TiO_2),has received much attention owing to its unique properties,such as structural disorder near the surface and the existence of Ti~(3+)ions and oxygen vacancies.Therefore,surface-disordered TiO_2has been applied for microwave absorption,photocatalysis,in photoelectrochemical sensors and rechargeable lithium-ion batteries.In this work B-TiO_2,a polymorph consisting of nanoparticles,nanotubes and nanosheets,was successfully synthesized and employed as a semiconductor layer in dye-sensitized solar cells(DSSCs)fabricated using a low-temperature heat treatment process(120°C).Based on the analyses of the experimental results regarding the structure and those from the characterization of B-TiO_2,and its application to DSSCs,it has been found that the B-TiO_2 material has an effect on electron-hole pair separation.The conversion efficiency of the B-TiO_2 DSSC(BTiO_2-DSSC)was 6.18%,whereas that of the TiO_2-P25 DSSC(P25-DSSC)was 3.61%,and that of the TiO_2 polymorph DSSC(PTiO_2-DSSC)which is the precursor of B-TiO_2 was 4.51%.