缺陷对Pt在Graphene上吸附影响的研究

本文利用第一原理方法计算了空位缺陷和硼（B）掺杂时对Pt在graphene上吸附的影响.结果表明：Pt在graphene上吸附的稳定位置是Pt吸附在桥位;悬挂键的存在极大的增强了Pt在graphene空位处的吸附;B替位掺杂有利于Pt原子在杂质附近的吸附.     

缺陷对Pt在Graphene上吸附影响的研究

本文利用第一原理方法计算了空位缺陷和硼（B）掺杂时对Pt在graphene上吸附的影响.结果表明：Pt在graphene上吸附的稳定位置是Pt吸附在桥位；悬挂键的存在极大的增强了Pt在graphene空位处的吸附；B替位掺杂有利于Pt原子在杂质附近的吸附.     

PtCu二元金属催化剂抗CO中毒性能的理论研究

基于密度泛函第一性原理研究了M-graphene(M=Pt,Cu,PtCu;graphene:pristine,Stonewales,Single-vacancy graphene)催化剂的抗CO中毒能力.对于纯Pt和纯Cu吸附在石墨烯上时,Pt的吸附能力最强,吸附结构最稳定.当Pt中掺杂Cu后,PtCu二元金属催化剂在石墨烯上的吸附结构的稳定性进一步增强.通过对M-graphene-CO吸附结构的研究,发现以缺陷石墨烯为载体的金属催化剂的抗CO中毒能力优于以原始石墨烯为载体的同种金属催化剂,PtCu二元金属催化剂抗CO中毒能力明显好于纯Pt和纯Cu的抗毒性.因此,缺陷石墨烯载体以及掺杂Cu的PtCu二元金属催化剂,对于提高催化剂的稳定性和抗CO中毒能力起到了重要的作用.     

Pt基电极材料硫中毒机理的计算机模拟研究

采用基于密度泛函理论的第一性原理方法和超原胞模型,计算并分析了Pt及Cu掺杂的Pt基合金的表面态密度,以及S在Pt及Pt基合金表面的吸附能和态密度情况.考虑了多种掺杂体系及吸附构型,结果表明：Cu掺杂会降低Pt基体系表面费米能级附近态密度,Pt皮肤的存在可以有效地减小Cu掺杂对体系表面态密度的影响;与S在纯Pt表面吸附相比较,S在掺杂体系表面的吸附能较小,且S的吸附对掺杂体系费米能级附近表面态密度影响较小. 以上研究结果有助于为改善Pt基电极材料的催化性能,尤其是其抗S中毒性能提供理论依据.     

S在Pt皮肤Pt3Ni(111)面吸附的第一性原理研究

采用基于密度泛函理论的第一性原理方法,计算并分析了S原子在 Pt皮肤Pt3Ni(111)面不同位置的吸附特性.结果表明：S原子在Pt皮肤Pt3Ni的fcc位吸附最强,吸附能为5. 49 eV;与S原子在纯净Pt(111)表面的吸附相比,S原子在Pt皮肤Pt3Ni表面相应吸附位置的吸附能变小、与近邻的Pt原子形成的S-Pt键变长,表明掺杂的Ni会减小相应位点S原子的吸附能,降低体系对S原子的吸附能力,进而减弱S吸附对体系催化能力的影响;态密度分析发现, S原子的吸附使得Pt基催化剂的催化活性降低,主要是S的2p电子引起的;这些结果将为后续研究Pt基合金电极抗S中毒效果以及探究S原子吸附后Pt3Ni的活性位提供依据.     

S在Pt皮肤Pt_3Ni(111)面吸附的第一性原理研究

采用基于密度泛函理论的第一性原理方法,计算并分析了S原子在Pt皮肤Pt3Ni(111)面不同位置的吸附特性.结果表明:S原子在Pt皮肤Pt3Ni的fcc位吸附最强,吸附能为5.49eV;与S原子在纯净的Pt(111)表面吸附相比较,S原子在Pt皮肤Pt3Ni(111)面相应吸附位置的吸附能变小,与近邻Pt原子形成的S-Pt键变长,表明掺杂的Ni会减小相应位点S原子的吸附能,降低体系对S原子的吸附能力,进而减弱S吸附对体系催化能力的影响;态密度分析发现,S原子的吸附使得Pt基催化剂的催化活性降低,主要是S的2p电子引起的;这些结果将为后续研究Pt基合金电极抗S中毒效果以及探究S原子吸附后Pt3Ni的活性位提供依据.     

Pt掺杂MoSe2吸附CF3I分解组分的第一性原理研究

CF₃I作为SF₆最具潜力的新型环保绝缘气体,在电气设备出现局部放电、过热等缺陷故障时,会产生C₂F₆和C₂F₄等强温室气体,为确保电力设备稳定运行,有必要对CF₃I典型分解组分吸附去除.本文基于密度泛函理论的第一性原理计算方法,通过吸附能、吸附距离、电荷转移和态密度等吸附指标,分别探究了不同数量Pt掺杂MoSe₂对C₂F₆和C₂F₄气体分子的吸附性能.研究结果表明：不同数量Pt掺杂在MoSe₂表面均存在稳定的掺杂结构,且相较本征MoSe₂,Pt掺杂后的MoSe₂导电性均得到了有效增强;Pt掺杂MoSe₂对CF₃I分解组分的吸附效果：Pt₂-MoSe₂>Pt-MoSe<...     

二氧化硫在改性BC_3表面的吸附特性研究

采用基于密度泛函理论的第一性原理方法观察修饰不同原子(Mo,Pt,Si)来调控BC_3体系的表面结构和反应活性.研究发现:单个原子吸附在BC_3表面具有不同的稳定位,Pt和Si原子吸附在H1位稳定,而Mo原子吸附在H2位稳定.单个原子在完整结构BC_3表面的扩散势垒较小,而掺杂的原子在单空位缺陷BC_3体系中具有极高的稳定性( 6.5 eV),这些掺杂原子显正电性能够有效地调制BC_3体系的电子结构、磁性以及影响二氧化硫(SO_2)的吸附强弱.与Pt原子掺杂的BC_3体系(Pt-BC_3)相比,单个SO_2分子在Si-和Mo-BC_3体系上的吸附能较大,表现出较高的灵敏特性.该研究为设计类石墨烯基功能纳米材料提供参考.     

第一性原理研究O2在CrN4掺杂石墨烯上的氢化

掺杂是调制graphene催化特性的有效方法. 掺杂的Graphene, 因其具有对氧还原反应具有较高的活性, 而作为一种新型高效质子交换膜燃料电池阴极材料. 采用包含色散力校正的第一性原理的密度泛函理论方法(DFT-D)系统的研究了O2在CrN4掺杂的Graphene上的吸附和氢化特性. 结果表明: (1) O2倾向于以side-on模式吸附在Cr顶位, 形成O-Cr-O三元环结构, 吸附能为1.75 eV; (2) O2在CrN4-Gra上更倾向于直接分解成O+O, 并进一步氢化为O+OH, 反应的限速步为O2的分解, 相应的反应势垒为0.48 eV.     

Structural,electronic,and magnetic behaviors of 5d transition metal atom substituted divacancy graphene:A first-principles study

Structural, electronic, and magnetic behaviors of 5d transition metal(TM) atom substituted divacancy(DV) graphene are investigated using first-principles calculations. Different 5d TM atoms(Hf, Ta, W, Re, Os, Ir, and Pt) are embedded in graphene, these impurity atoms replace 2 carbon atoms in the graphene sheet. It is revealed that the charge transfer occurs from 5d TM atoms to the graphene layer. Hf, Ta, and W substituted graphene structures exhibit a finite band gap at high symmetric K-point in their spin up and spin down channels with 0.783 μB, 1.65 μB, and 1.78 μB magnetic moments,respectively. Ir and Pt substituted graphene structures display indirect band gap semiconductor behavior. Interestingly, Os substituted graphene shows direct band gap semiconductor behavior having a band gap of approximately 0.4 e V in their spin up channel with 1.5 μB magnetic moment. Through density of states(DOS) analysis, we can predict that d orbitals of 5d TM atoms could be responsible for introducing ferromagnetism in the graphene layer. We believe that our obtained results provide a new route for potential applications of dilute magnetic semiconductors and half-metals in spintronic devices by employing 5d transition metal atom-doped graphene complexes.     

Point defects on graphene on metals

Understanding the coupling of graphene with its local environment is critical to be able to integrate it in tomorrow's electronic devices. Here we show how the presence of a metallic substrate affects the properties of an atomically tailored graphene layer. We have deliberately introduced single carbon vacancies on a graphene monolayer grown on a Pt(111) surface and investigated its impact in the electronic, structural, and magnetic properties of the graphene layer. Our low temperature scanning tunneling microscopy studies, complemented by density functional theory, show the existence of a broad electronic resonance above the Fermi energy associated with the vacancies. Vacancy sites become reactive leading to an increase of the coupling between the graphene layer and the metal substrate at these points; this gives rise to a rapid decay of the localized state and the quenching of the magnetic moment associated with carbon vacancies in freestanding graphene layers.     

基于Matlab分析负荷对多联机IPLV的影响

多联机有其特殊的优点,但是不同部分负荷的组合对IPLV的影响仍需进一步研究。文中建立IPLV与部分负荷的相关公式,运用MATLAB软件分析不同卸载级负荷与IPLV的关系,从而确定不同部分负荷的最优组合。     

Remarks on KdV-type flows on star-shaped curves

We study the relation between the centro-affine geometry of star-shaped planar curves and the projective geometry of parametrized maps into RP¹. We show that projectivization induces a map between differential invariants and a bi-Poisson map between Hamiltonian structures. We also show that a Hamiltonian evolution equation for closed star-shaped planar curves, discovered by Pinkall, has the Schwarzian KdV equation as its projectivization. (For both flows, the curvature evolves by the KdV equation.) Using algebro-geometric methods and the relation of group-based moving frames to AKNS-type representations, we construct examples of closed solutions of Pinkall’s flow associated with periodic finite-gap KdV potentials.     

Note on duality on polarized symplectic manifolds

In this note we use some of the results of [3] to derive a general duality theorem for the cohomologies of foliated structures on a manifold. The result is applied to the special case of a symplectic manifold M on which the foliation is given by a complex polarization F in the sense of geometric quantization. We obtain, for example, a rigorous proof of the fact that for a smooth function ƒ on M whose Hamiltonian vector field leaves F invariant, the spectrum of the corresponding prequantization operator v(ƒ) coincides with the spectrum of its transpose, under the above duality. This latter result was obtained by Simms in [12] under certain hypotheses. Proofs of the validity of those hypotheses are now available in the literature; cf. [3] and [7].     

Space-charge effects on multipactor on a dielectric

Analyzes the effects of space charge shielding on the steady state of a multipactor discharge on a dielectric. Analytic methods are used to obtain an exact function for the potential in the discharge, assuming a Maxwellian distribution of emitted electrons. An equation for the amount of power deposited on the dielectric by the multipactoring electrons, for a given saturation level, is given. A simple method for obtaining the saturation level, for a given material, is obtained