首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 93 毫秒
1.
LiFePO4 晶格动力学性质的第一性原理研究   总被引:1,自引:0,他引:1       下载免费PDF全文
忻晓桂  陈香  周晶晶  施思齐 《物理学报》2011,60(2):28201-028201
基于考虑了Fe-3d电子间的库仑作用U和交换作用J的GGA+U方案,应用第一性原理计算系统研究了LiFePO4的晶格动力学性质.我们计算并分析了玻恩有效电荷张量、布里渊区中心的声子频率和声子色散曲线.玻恩有效电荷张量显示各向异性,佐证了LiFePO4中锂离子沿一维通道[010]方向迁移的机理.布里渊区中心点声子频率的计算值和相应的实验结果符合得比较好. 关键词: 4')" href="#">LiFePO4 晶格动力学 第一性原理计算  相似文献   

2.
崔冬萌  谢泉  陈茜  赵凤娟  李旭珍 《物理学报》2010,59(3):2027-2032
采用基于第一性原理的赝势平面波方法,对异质外延关系为Ru2Si3 (100)//Si(001),取向关系为Ru2Si3[010]//Si[110]正交相的Ru2Si3平衡体系下的能带结构、态密度和光学性质等进行了理论计算.计算结果表明:当晶格常数a取值为1093 nm时,正交相Ru2Si3处于稳定状态并且是具有带隙值 关键词: 外延 第一性原理 电子结构 光学性质  相似文献   

3.
OsSi2电子结构和光学性质的研究   总被引:1,自引:0,他引:1       下载免费PDF全文
李旭珍  谢泉  陈茜  赵凤娟  崔冬萌 《物理学报》2010,59(3):2016-2021
采用基于第一性原理的密度泛函理论赝势平面波方法,对正交相OsSi2的电子结构、态密度和光学性质进行了理论计算,能带结构计算表明它是一种间接带隙半导体,禁带宽度为0813 eV;其价带主要由Os的5d和Si的3p态电子构成;导带主要由Si的3s,3p以及Os的5d态电子构成;静态介电常数ε1(0)=1543; 折射率n=393并利用计算的能带结构和态密度分析了OsSi2的介电函数、吸收系数、折射率、反射率、 关键词: 2')" href="#">OsSi2 第一性原理 电子结构 光学性质  相似文献   

4.
陈海川  杨利君 《物理学报》2011,60(1):14207-014207
采用基于第一性原理的密度泛函理论赝势平面波方法,对LiGaX2(X=S, Se, Te)的能带结构、态密度、光学以及弹性性质进行了理论计算. 能带结构计算表明LiGaS2 的禁带宽度为4.146 eV, LiGaSe2 的禁带宽度为3.301 eV, LiGaTe2 的禁带宽度为2.306 eV; 其价带主要由Ga-4p 层电子和X- np 层电子的能态密度决定; 同时也对LiGaX< 关键词: 电子结构 光学性质 弹性性质 LGX  相似文献   

5.
使用密度泛函第一性原理研究了超导体MgB2单晶各向异性的光学性质.在描述光学性质的基本理论和计算方法的基础上,计算了MgB2的光电导谱、反射谱以及电子能量损失谱,并通过MgB2的各个原子分解态密度图对所得到的反射谱和损失谱的各个谱峰做了详尽地分析.从光电导谱上来看,x方向与z方向有着很大差别,而在反射谱与电子能量损失谱中,x方向与z方向的特征峰位置都是相互符合的.从光导谱来看,沿 关键词: 超导体 电子结构 光学性质  相似文献   

6.
张计划  丁建文  卢章辉 《物理学报》2009,58(3):1901-1907
基于密度泛函理论(DFT)的第一性原理平面波超软赝势方法,计算了Co掺杂MgF2晶体的几何结构、电子结构和光学性质.结果表明,Co掺杂导致MgF2晶体结构畸变,可能发生一种类四方和斜方型结构相变.由于Co原子的加入,体系的禁带宽度减小,可观察到半导体—金属性转变.计算也表明,Co掺杂对静态介电常数和光吸收系数有重要调制作用,所得结果与最近实验测量很好相符,揭示了Co:MgF2体系在光学元器件方面的潜在应用. 关键词: 密度泛函理论(DFT) 第一性原理 超软赝势 2')" href="#">Co掺杂MgF2  相似文献   

7.
章瑞铄  刘涌  滕繁  宋晨路  韩高荣 《物理学报》2012,61(1):17101-017101
采用基于密度泛函理论的第一性原理计算了锐钛矿相和金红石相TiO2:Nb的晶体结构、电子结构和光学性质. 结果表明, 在相等的摩尔掺杂浓度下(6.25%), 锐钛矿相TiO2:Nb的导带底电子有效质量小于金红石相TiO2:Nb, 且前者室温载流子浓度是后者的两倍左右, 即具有更大的施主杂质电离率, 从而解释了锐钛矿相TiO2:Nb比金红石相TiO2:Nb具有更优异电学性能的实验现象. 光学计算也表明锐钛矿相在可见光区有更大的透过率, 从而在理论上解释了锐钛矿相TiO2:Nb比金红石相TiO2:Nb更适于做透明导电材料的原因. 计算结果与实验数据能较好符合. 关键词: 2:Nb')" href="#">TiO2:Nb 第一性原理 电子结构 光学性能  相似文献   

8.
S掺杂对锐钛矿相TiO2电子结构与光催化性能的影响   总被引:2,自引:0,他引:2       下载免费PDF全文
赵宗彦  柳清菊  朱忠其  张瑾 《物理学报》2008,57(6):3760-3768
采用基于第一性原理的平面波超软赝势方法研究了掺杂不同价态S的锐钛矿相TiO2的晶体结构、杂质形成能、电子结构及光学性质.计算结果表明硫在掺杂体系中的存在形态与实验中的制备条件有关;掺杂后晶格发生畸变、原子间的键长及原子的电荷量也发生了变化,导致晶体中的八面体偶极矩增大; S 3p态与O 2p态、Ti 3d态杂化而使导带位置下移、价带位置上移及价带宽化,从而导致TiO2的禁带宽度变窄、光吸收曲线红移到可见光区.这些结果很好地解释了S掺杂锐钛矿相TiO2在可见光下具有优良的光催化性能的内在原因.根据计算结果分析比较了硫以不同离子价态掺杂对锐钛矿相TiO2电子结构和光催化性能影响的差别. 关键词: 2')" href="#">锐钛矿相TiO2 S掺杂 第一性原理 光催化性能  相似文献   

9.
周康  冯庆  田芸  李科  周清斌 《计算物理》2018,35(6):702-710
采用密度泛函理论(DFT)体系广义梯度近似(GGA)第一性原理平面波超软赝势方法,分析锐钛矿型TiO2(101)表面吸附NO2分子光学气敏传感的微观机理.结果表明:Cu和Cr原子易于掺入TiO2(101)表面,掺杂表面能稳定地吸附NO2分子且吸附后光学性质发生显著变化.表面吸附NO2分子后,Cu掺杂TiO2(101)表面对分子的吸附能最大,吸附后结构更稳定,分子与表面的距离最短.通过分析差分电荷密度和电荷布居数发现,NO2分子与基底表面间发生电荷转移,转移电子数目:Cu掺杂表面 > Cr掺杂表面 > 无掺杂表面.对比吸收光谱和反射光谱发现,在Cu掺杂表面吸附分子后,光学性质变化最明显,说明表面与吸附分子间氧化还原能力是决定光学气敏传感性能的核心因素.在过渡金属中,Cu与Cr都有4s价电子结构,其4s电子降低了材料表面氧空位的氧化性,增加了其还原性.对于氧化性气体,可以提升表面与分子的氧化还原作用,而Cu的4s电子更加活泼,从而光学气敏传感特性更加明显.因此,Cu掺杂的TiO2对氧化性气体是一种较好的光学气敏传感材料.  相似文献   

10.
利用第一性原理计算了立方相萤石TiO2的晶胞参数,能带结构和电子态密度.结果显示萤石TiO2属于间接带隙半导体材料,其间接禁带宽度(ΓX)Eg为2.07eV,比常见的金红石和锐钛矿TiO2的禁带宽度窄.为了更清楚地了解萤石的光学性质,利用Kramers-Kronig色散关系,分别对萤石和金红石TiO2的复介电常数、吸收率等参数进行了计算,并将二者结果做了 关键词: 2')" href="#">萤石结构TiO2 密度泛函理论 能带结构 光学性质  相似文献   

11.
利用倾斜衬底沉积法在无织构的金属衬底上生长了MgO双轴织构的模板层,在这一模板层上实现了YBa2Cu3O7-x薄膜的外延生长.在外延YBa2Cu3O7-x薄膜前,依次沉积了钇稳定的立方氧化锆和CeO2作为缓冲层.利用X射线衍射2θ扫描、扫描、Ω扫描和极图分析测定了这些膜的结构和双轴织 关键词: 2Cu3O7-x镀膜导体')" href="#">YBa2Cu3O7-x镀膜导体 2缓冲层')" href="#">CeO2缓冲层 厚度依赖性 外延生长  相似文献   

12.
双钙钛矿SrKFeWO6的电子结构与磁性   总被引:1,自引:0,他引:1       下载免费PDF全文
张瑜  刘拥军  刘先锋  江学范 《物理学报》2010,59(5):3432-3437
基于密度泛函理论框架下的第一性原理,采用考虑在位库仑作用的广义梯度近似(GGA+U)下的投影缀加波(PAW)方法,研究了具有双钙钛矿结构的Sr2FeWO6和SrKFeWO6材料的晶体结构、电子结构以及磁性性质.结构优化表明,K空穴掺杂稳定了FeO6及WO6八面体结构,Fe-O-W键角更加接近180°,有利于Fe-O-W-O-Fe超交换作用;对电子结构分析发现掺杂元素本身对总态密度贡献很小,空穴(p 关键词: 电子结构 磁性 6')" href="#">SrKFeWO6 双钙钛矿  相似文献   

13.
The lattice parameters, band structure, density of state and elastic constant of RE-doped CeO2 (RE=Sm, Gd, Dy), the buffer material for coated HTS conductors, are calculated using the plane-wave method with pseudopotentials based on the density functional theory (DFT) of first-principle. The rule and mechanism of the effect of rare earth impurity on the critical thickness of the CeO2 buffer layer are investigated. It is found that, in the range of the calculation, the changes of the lattice volume V and elastic constant E* of CeO2 with the impurity are mainly determined by the increased electrons δn e of the system. The relationship of the elastic constant E* and increased electrons δn e is established. It is indicated that the critical thickness of the CeO2 single buffer layer doped with Sm, Gd, and Dy may be enhanced by 22%, 43% and 33%, respectively. Supported by the Youth Scientific Research Project of Southwest Jiaotong University (Grant No. 2007Q017), the National Natural Science Foundation of China (Grant No. 50588201), and the Ministry of Science and Technology of China (Grant No. 2007CB616906)  相似文献   

14.
Nanocrystalline NiO–CeO2 binary oxide as a novel electrode material for ultracapacitor was synthesized via glycol assisted citrate sol–gel method. Unique cubic phases with aggregated crystalline microstructure of NiO–CeO2 mixed oxides were examined by X-ray diffraction and transmission electron microscope. The observed electrochemical measurements further reveal the strong pseudocapacitance features of the mixed oxides at different current density. Binary oxide annealed at 500 °C shows an optimum specific capacitance (C s ) of 305 Fg?1 at the constant current density of 1 Ag?1. The achieved C s value undoubtedly certifies that in combination with NiO the structural stability and redox property of CeO2 have been enhanced. Especially, increasing the calcination temperature binary oxide has shown well reversible redox features which confirm the high chemical and thermal stability of CeO2 and it could be involve in the charge storage process effectively by their strong Ce3+/Ce4+ redox couples. Capacity retention and cyclic stability of the electrode was quite good, only ~5 % capacity fading was observed after 1,000 cycles. Moreover, binary oxide calcined at 700 °C exhibits a specific capacitance of 167 Fg?1 at the constant current density of 1 Ag?1 which states that presence of CeO2 with NiO have controlled the grain growth and maintains their porous microstructure even at 700 °C. This facilitates to the redox process at both NiO and CeO2 active surfaces at elevated temperature significantly.  相似文献   

15.
Cerium oxide nanoparticles and cerium oxide nanoparticle-decorated graphene oxide (GO) are synthesized via a facile chemical coprecipitation method in the presence of hexadecyltrimethylammonium bromide (CTAB). Nanostructure studies and electrochemical performances of the as-prepared samples were systematically investigated. The crystalline structure and morphology of the nanocomposites were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy (TEM), Raman spectrum, and X-ray photoelectron spectroscopy (XPS). Electrochemical properties of the CeO2 electrode, the GO electrode, and the nanocomposites electrodes were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements. The CeO2 nanoparticle-decorated GO (at the mole ratio of CeO2/GO = 1:4) electrode exhibited excellent supercapacitive behavior with a high specific capacitance of 382.94 F/g at the current density of 3.0 A/g. These superior electrochemical features demonstrate that the CeO2 nanoparticle-decorated GO is a promising material for next-generation supercapacitor systems.  相似文献   

16.
In the present study, the effect of the addition of boron on the electrical conduction properties of nanocrystalline cerium oxide (CeO2) was investigated. Pellets consisting of pure CeO2 and a mixture of CeO2 and 10 mol.% of boron oxide (B-CeO2 samples) were sintered at 800 °C as well as 1100 °C and their electrical conduction properties investigated by impedance spectroscopy at different temperatures and oxygen partial pressures. The nanocrystalline B-CeO2 samples exhibit a higher electronic grain boundary conductivity and higher activation energy compared to a pure CeO2 sample (1.41 eV for B-CeO2 vs. 1.21 eV for pure CeO2). According to electron energy-loss spectroscopy analysis, (i) boron can be detected only at the grain boundaries and (ii) cerium cations are lightly reduced at the grain boundaries. The results are consistent with both the formation of a space charge layer with a positive space charge potential but also with conduction along a glassy cerium-boron-oxide phase.  相似文献   

17.
Here, we investigate the band structure, density of states, photocatalytic activity, and heterojunction mechanism of WS2 with CeO2 (CeO2@WS2) as a photoactive heterostructure. In this heterostructure, CeO2′s growth within WS2 layers is achieved through ultrasonicating WS2 and intercalating CeO2′s precursor within the WS2 interlayers, followed by hydrothermal treatment. Through a set of density functional calculations, we demonstrate that CeO2 and WS2 form an interface through a covalent bonding that can be highly stable. The electrochemical impedance spectroscopy (EIS) found that the CeO2@WS2 heterostructure exhibits a remarkably higher conductivity (22.23 mS cm−2) compared to either WS2 and CeO2, assignable to the interface in CeO2@WS2. Furthermore, in a physically mixed CeO2-WS2 where the interaction between particles is noncovalent, the resistance was significantly higher (0.67 mS cm−2), confirming that the heterostructure in the interface is covalently bonded. In addition, Mott-Schottky and the bandgap measurements through Tauc plots demonstrate that the heterojunction in CeO2 and WS2 is type II. Eventually, the CeO2@WS2 heterostructure indicated 446.7 µmol g −1 CO2 generation from photocatalytic oxidation of a volatile organic compound (VOC), formic acid, compared to WS2 and CeO2 alone.  相似文献   

18.
The CeO2/TiO2 and TiO2/CeO2 interface composite films were prepared on glass substrates by the sol-gel process via dip-coating and calcining technique. The scanning electron microscopy (SEM) revealed that the TiO2 layer has a compact and uniformity glasslike surface with 200 nm in thickness, and the CeO2 layer has a coarse surface with 240 nm in thickness. The X-ray diffractometer (XRD) analysis showed that the TiO2 layer is made up of anatase phase, and the CeO2 layer is structured by cubic fluorite phase. Through a series of photo-degradation experiments, the relationship of the photocatalytic activity with the constituents of the films was studied. In virtue of the efficient interfacial charge separation via the process of electron transfer from TiO2 to CeO2, the photocatalytic activity of the CeO2/TiO2 composite film is high. Contrarily, the photocatalytic activity of the TiO2/CeO2 composite film is low, due to its inert surface made up of CeO2 with broad bandwidth. Apart from the effect of the film structure, the effect of film thickness on photocatalytic activity was also discussed.  相似文献   

19.
CeO2 nanostructures were successfully prepared by a facile and environmentally friendly mixed-solvothermal method under mild conditions. The X-ray diffraction (XRD) and transmission electron microscope (TEM) results indicated that the as-synthesized products were cubic CeO2 polycrystalline structures with uniform diameters in the range of 10–20 nm and lengths up to 80 nm. X-ray photoelectron spectroscopy (XPS) spectra and EDX data demonstrated that stoichiometric CeO2 was formed. A possible growth mechanism of the CeO2 nanostructures was proposed. Moreover, ultraviolet absorption measurement revealed the band gap of the CeO2 nanorods was estimated to be 3.85 eV, which is larger than the reported value for the bulk CeO2 (Eg=3.2 eV). Enhancement of the band gap of the CeO2 nanorods is attributed to the well-known quantum size effect.  相似文献   

20.
Ni sintering at high temperature (~ 800 °C) operation drastically degrades the performance of Ni-yttria-stabilized zirconia (YSZ) anode in solid oxide fuel cell (SOFC). Mixed ionic and electronic conductive oxides such as CeO2 and Nb2O5 enhance the dispersion of Ni, CeO2 enhances the redox behavior and promotes charge transfer reactions, and Nb2O5 increases the triple phase boundary. In the present work, anode-supported SOFC is fabricated and tested in H2 fuel at 800 °C. YSZ and lanthanum strontium manganite (LSM)-YSZ are used as the electrolyte and composite cathode with NiO-YSZ, CeO2-NiO-YSZ, and Nb2O5-NiO-YSZ as an anode. The peak power density obtained for the cell with 10% CeO2–30% NiO-YSZ anode at the 5 and 25 h of operation is 330 and 290 mW cm?2 which is higher than that for 40% NiO-YSZ anode (275 mW cm?2 at 5 h). The peak power density obtained for the cell with 10% Nb2O5–30% NiO-YSZ anode at the 5 and 25 h of operation is 301 and 285 mW cm?2 which is higher than that for 40% NiO-YSZ anode (275 mW cm?2 at 5 h). Physical characterization has been carried to study morphology, elemental analysis, particle size, and phase formation of the fabricated anode before and after cell operation to correlate the cell performance.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号