Cu(Ⅱ)掺杂锐钛矿TiO_2第一性原理研究

采用基于密度泛函理论(DFT)框架下的第一性原理平面波赝势(PWPP)方法,模拟计算了Cu(II)掺杂锐钛矿TiO2,讨论了Cu(II)掺杂对锐钛矿的晶体结构、能隙、态密度等的影响。结果表明Cu(II)掺杂锐钛矿TiO2晶体后,Cu-3d与O-2p轨道上的电子发生强烈关联作用,使O-2p轨道发生分裂,禁带宽度(Eg)变小,TiO2的吸收带红移,从而有助于TiO2的光催化活性。     

PbSe(001)表面特性的第一性原理研究

用第一性原理的密度泛函理论计算了PbSe（001）表面的几何结构和电子特性。计算结果表明：PbSe（001）表面几层原子出现明显的振荡弛豫现象,但没发生重构,第一、二原子间距减小,第二、三层原子间距增大,同时也发现表面层原子出现褶皱。该表面的直接带隙出现在X点,在导带底和价带顶附近出现4个表面共振态,另外两个表面态分别出现在-4．0eV附近和-11．5eV附近。     

高压下超导体FeSe电子结构的第一性原理研究

从头计算了高压下超导体FeSe体相的性质,参数设定和性质计算都基于密度泛函理论,交换相关能采用GGA,泛函形式为PBE,原子间相互作用的描述采用超软赝势。计算发现压力使FeSe4四面体发生畸变,Fe的3d轨道劈裂为t2g轨道和eg轨道,并且Fe的d轨道劈裂能在一定压力范围随压力增加而变大,其中t2g电子具有空穴的导电特征,eg电子为电子导电特征;在费米面附近Fe的3d电子的态密度与总能态密度几乎相等,说明物质的超导电性源于同一层之间的Fe2+的相互作用。     

AlN(10-10)表面结构的第一性原理计算

采用基于密度泛函理论的第一性原理方法,计算了六方AlN及其(10-10)表面的原子及电子结构.其中计算出的六方AlN晶体中的晶格常数和体弹性模量与实验值很符合.用平板超原胞模型模拟计算AlN(10-10)表面的原子及电子结构,结果表明:AlN(10-10)表面弛豫后,表面顶层原子之间的键长收缩并发生扭转.表面原子均向体内移动,原子轨道重新杂化,N原子趋向于p3构型,Al原子趋向于sp2构型.     

La、Sb共掺杂SnO 2电性能的第一性原理研究

基于密度泛函理论的第一性原理方法,使用软件构建了Sb、La单掺杂与共掺杂SnO2的超晶胞模型,几何优化并计算分析其晶体结构、能带结构、态密度及布居.结果显示:与单掺杂比,La-Sb共掺后的热稳定性最高,仍是直接带隙材料.Sb的5 s、5 p态和La的5 p态在导带底引入杂质能级,使得导带下移,带隙变小,载流子跃迁所需的...     

钽掺杂金红石TiO2电子结构的第一性原理研究

采用第一性原理中的CASTEP模块计算了金红石相TiO2掺杂过渡金属钽元素的能带结构以及态密度。计算结果表明，Ta原子替换Ti原子后，Ta的5d轨道对TiO2的导带影响较明显，且使TiO2的带隙宽度减小，这样有可能使金红石TiO2吸收带出现红移现象或产生在可见光区的吸收，其中Ta原子的t2g态起了重要作用。     

Cu掺杂SnO2(110)面对CO气敏机理的第一性原理研究

基于密度泛函理论的第一性原理计算,研究了有毒气体CO在本征和Cu掺杂SnO_2(110)面不同原子位的吸附,通过对吸附能的比较得出了最佳吸附位置及吸附结构。计算结果表明,本征SnO_2(110)面对CO的吸附很弱。而对于Cu掺杂SnO_2的(110)面,掺杂浓度选2.7%和5.4%两组,分别用Sn_(15)CuO_(24)和Sn_(14)Cu_2O_(24)表示。通过比较本征和不同Cu掺杂浓度下SnO_2(110)面上CO的吸附能和电荷布居,发现Cu掺杂可显著提高CO的吸附性能,其中Cu掺杂浓度为5.4%的Sn_(14)Cu_2O_(24)表面的吸附活性位点增加,吸附效果最好。     

磷掺杂金红石TiO2电子结构的第一性原理研究

TiO2作为一种光催化材料,具有广阔的应用领域.近几年,利用掺杂改性来改善TiO2光催化性已成为当今研究的热点.本文采用第一性原理方法和超晶胞模型计算了磷元素掺杂金红石相TiO2的电子结构,并分析了三种不同掺杂位置的电子结构对TiO2光催化性能的影响.计算结果表明,P置换O和P在晶格间隙位置的掺杂对TiO2的带隙影响比较明显,在带隙中均形成了中间掺杂能级,都有可能使TiO2吸收带出现红移现象或产生在可见光区的吸收,但P在晶格间隙位置的掺杂所形成的中间掺杂能级比较平稳,有可能改善TiO2光催化性能,其中磷原子的3p态起了重要作用.     

纳米掺杂SnO2的研究及其第一性原理的计算

利用Castap软件计算了Co以不同比例掺杂SnO2的电子结构，分析了掺杂及掺杂比例对改善SnO2导电性的作用，建立了纯SnO2计算模型。计算结果表明：纯SnO2是一种包含离子键的共价键直接禁带半导体；通过掺杂能够在一定程度上改变成键性质，使其具有金属键性质，从而提高SnO2导电性。其中，掺杂比率为5％的价带到中间能级宽度最小，掺杂原子与其邻近原子的电荷重叠区更明显，系统电子共有化程度最高，费米能级处对电子态密度的贡献也最大，因此掺杂比率为5％的导电性最好。     

Ni掺杂PtAl2合金电子结构的第一性原理计算

采用第一性原理的密度泛函理论方法从杂质形成能、电荷布居、电子结构等几个方面研究了PtAl2合金的掺杂效应。结果发现,Ni置换Pt元素掺杂形成能的绝对值要低于Ni置换A1的掺杂形成能。进一步从电子结构分析,两者在费米面附近的电子主要是由Pt的4p电子轨道,Ni的3d电子轨道以及部分Al的3p电子轨道上的电子贡献,但前者在费米能附近的反应剧烈程度要高于后者,这说明在PtAl2合金的掺杂中,Ni元素更容易置换Pt原子与Al生成NiAl合金。     

Writing with atoms: Oxygen adatoms on the MoO2/Mo(110) surface

Writing at the nanoscale using the desorption of oxygen adatoms from the oxygen-rich MoO_2+x /Mo(110) surface is demonstrated by scanning tunnelling microscopy (STM). High-temperature oxidation of the Mo(110) surface results in a strained, bulk-like MoO₂(010) ultra-thin film with an O-Mo-O trilayer structure. Due to the lattice mismatch between the Mo(110) and the MoO₂(010), the latter consists of well-ordered molybdenum oxide nanorows separated by 2.5 nm. The MoO₂(010)/Mo(110) structure is confirmed by STM data and density functional theory calculations. Further oxidation results in the oxygen-rich MoO_2+x /Mo(110) surface, which exhibits perfectly aligned double rows of oxygen adatoms, imaged by STM as bright protrusions. These adatoms can be removed from the surface by scanning (or pulsing) at positive sample biases greater than 1.5 V. Tip movement along the surface can be used for controlled lithography (or writing) at the nanoscale, with a minimum feature size of just 3 nm. By moving the STM tip in a predetermined fashion, information can be written and read by applying specific biases between the surface and the tip.      

Cr2O3对(Co,Ta)掺杂的SnO2压敏电阻电学特性的影响

研究了Cr对(Co,Ta)掺杂的SnO2压敏材料电学性质的影响.当Cr2O3的含量从0增加到0.15mol%时,(Co,Ta)掺杂SnO2压敏电阻的击穿电压从206V/mm增加到493V/mm;1kHz时的相对介电常数从1968猛降至498;晶界势垒高度分析表明,SnO2晶粒尺寸的迅速减小是样品击穿电压增高、相对介电常数急剧降低和电阻率迅速增大的主要原因.对Cr含量增加引起SnO2晶粒减小的原因进行了解释.掺杂0.15mol% Cr2O3的SnO2压敏电阻非线性系数为24,击穿电压达498V/mm,在高压保护领域有很好的应用前景.     

Hysteresis properties of the two-dimensional structure of domain walls in magnetically triaxial films with a (110)-oriented surface plane

Structural transformations of a two-vortex asymmetric domain wall in a magnetically triaxial film with Goss-oriented (110) surface and cubic anisotropy have been studied by numerical micromagnetic simulation. It is established that transformations of the domain wall structure exhibit significant hysteresis that is accompanied by the related hysteresis of magnetization reversal in a field applied perpendicular to the easy magnetization axis.     

Graphene oxide (GO)-doping SnO2 flower-like structure to enhance photocatalytic activity

The GO/SnO₂ micronanostructure was synthesized by a simple and effective hydrothermal method. The combined characterization methods such as Scanning Electron Microscope (SEM), Transmission electron microscope (TEM), X-ray diffraction (XRD), Element mapping, Energy Dispersive X-Ray Spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), the Raman spectroscopy, the Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), photoluminescence (PL) the Ultraviolet–visible spectroscopy (UV-Vis) and Diffuse reflectance spectrum (DRS) indicated the successful formation of GO/SnO₂ micronanostructure. Moreover, the photocatalytic activity tested with RhB aqueous solution revealed that GO/SnO₂ had excellent photocatalytic properties compared with SnO₂. The photocatalytic efficiency of GO/SnO₂ was much higher (about 2.5 times) than that of pure SnO₂ under visible light irradiation. Based on these test results, we believe that the present work will provide some thoughts for further fabrication of other novel nanostructures and exploration of their applications.     

Self-Assembly and Ordering of C60 on the WO2/W（110） Surface

The growth and ordering of C₆₀ molecules on the WO₂/W(110) surface have been studied by low-temperature scanning tunnelling microscopy and spectroscopy (STM and STS), low-energy electron diffraction (LEED), and density functional theory (DFT) calculations. The results indicate the growth of a well-ordered C₆₀ layer on the WO₂/W(110) surface in which the molecules form a close-packed hexagonal structure with a unit cell parameter equal to 0.95 nm. The nucleation of the C₆₀ layer starts at the substrate’s inner step edges. Low-temperature STM of C₆₀ molecules performed at 78 K demonstrates well-resolved molecular orbitals within individual molecules. In the C₆₀ monolayer on the WO₂/W(110) surface, the molecules are aligned in one direction due to intermolecular interaction, as shown by the ordered molecular orbitals of individual C₆₀. STS data obtained from the C₆₀ monolayer on the WO₂/W(110) surface are in good agreement with DFT calculations.     

CuO掺杂对 SnO2压敏材料性能的影响

研究了掺杂 CuO对 SnO2· Ni2O3· Ta2O5压敏材料电学性能的影响.实验发现,随着 CuO的 掺杂量从 0.50mol%增加到 1.50mol%,材料的压敏电场强度从 132V/mm升高到 234V/mm,相对 介电常数从 4663减小到 2701.电场强度变化的原因是 CuO掺杂引起的晶粒尺寸变化,随掺杂量 增加晶粒尺寸从 18.8μ m减小到 13.3μ m.未固溶于 SnO2晶格而偏析在晶界上的 CuO阻碍了相 邻 SnO2晶粒的融合 ,这导致了晶粒尺寸的减小.为了解释 SnO2· Ni2O3· Ta2O5· CuO电学非线性 性质的起源,本研究对前人的晶界缺陷势垒模型进行了修正.对该压敏材料进行了等效电路分析, 实验测量与等效电路分析结果相符.     

Preparation of the SnO2/SiO2 xerogel with a large specific surface area

SnO₂/SiO₂ nanocomposite xerogel was synthesized by using the about-to-gel silica sol as “nanoglue”. Tin oxide uniformly dispersed within the three-dimension network of the silica in the form of nanoparticles. The SnO₂/SiO₂ nanocomposite xerogel has a large specific surface area (SSA), which depends on the deposition time of the silica sol.