共查询到19条相似文献,搜索用时 78 毫秒
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碳富勒烯包合物由于潜在的应用前景受到广泛关注.我们采用第一性原理方法计算了氢、氮、锂、铍原子在不同碳富勒烯中的吸附和穿越.根据原子在不同碳富勒烯笼中的势能曲线,我们给出了原子穿越碳富勒烯笼的势垒和势阱,归纳出原子穿越碳笼机理分为插入机理、渗透机理以及插入机理和渗透机理的混合机理. 相似文献
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基于第一性原理计算方法,对Ni_xAg_y(x+y=13)团簇的几何结构进行优化后,研究了NO在此类团簇表面不同位置的吸附分解行为,讨论了团簇的束缚能、束缚能的二阶差分、能隙以及吸附前后键长、吸附能、NO分波态密度的变化情况.结果表明,团簇对称性随着Ni的占比变化而变化,稳定性随Ni占比增加而增强,束缚能的二阶差分随着Ni原子的增多呈现奇偶震荡性,NO@Ni_xAg_y(x+y=13)团簇表面吸附行为主要为化学吸附,吸附后N-O键长的变化在0.028?~0.092?之间.对团簇吸附NO的态密度分析发现,吸附后NO的2π*轨道失去电子,1π轨道得到电子,从而导致吸附能的变化. 相似文献
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本文采用基于密度泛函理论(DFT)的第一原理赝势平面波(PW-PP)方法,对氢分子在Mg2Ni(010)面的吸附与分解进行了研究,发现氢分子以Horl的方式吸附在表面层Ni原子的顶位时吸附能最高,为0.6769 eV,这表明氢分子最可能以Horl的方式吸附在表面层Ni原子的顶位,此时氢分子跟表面的距离(rd)和氢分子的键长(rH)分别为1.6286 A和0.9174 (A).在分子吸附的基础上计算了氢分子沿着选取的反应路径分解时的反应势垒,发现要使氢分子分解需要0.2778 eV的活化能,而氢分子分解时的吸附能为0.8390 eV,分解后两个氢原子的距离为3.1712(A).在分子吸附和分解吸附时氢原子跟正下方的Ni原子都有较强的相互作用,氢原子所得到的电子主要来自氢分子正下方的Ni原子. 相似文献
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本文采用基于密度泛函理论(DFT)的第一原理赝势平面波(PW-PP)方法,对氢分子在Mg2Ni(010)面的吸附与分解进行了研究,我们发现氢分子以Hor1的方式吸附在表面层Ni原子的顶位时吸附能最高,为0.6769eV,这表明氢分子最可能以Hor1的方式吸附在表面层Ni原子的顶位,此时氢分子跟表面的距离( )和氢分子的键长( )分别为1.6286Å和0.9174Å. 在分子吸附的基础上计算了氢分子沿着选取的反应路径分解时的反应势垒,发现要使氢分子分解需要0.2778eV的活化能,而氢分子分解时的吸附能为0.8390eV,分解后两个氢原子的距离为3.1712Å. 在分子吸附和分解吸附时氢原子跟正下方的Ni原子都有较强的相互作用,氢原子所得到的电子主要来自氢分子正下方的Ni原子. 相似文献
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基于第一性原理计算方法,对含空位缺陷的V2C(MXene)在不同位点修饰单原子Al的相关性能进行系统研究.研究表明,几何优化后得到含空位缺陷的V2C稳定结构表面能为-3075.53 J/m2,单原子Al修饰本征V2C单原子的吸附能为1.5511eV、单原子Al修饰空位缺陷V2C的吸附能为-2.0763 eV,这表明含空位缺陷的V2C,由于单原子Al的修饰可以明显改善晶体结构稳定性.进一步从态密度、分波态密度、吸氢能力研究发现,各体系态密度和分波态密度均出现分波越过费米能级的现象,表现出较强的金属性;V2C吸附H2气体分子吸附能为-7.5867 eV,而空位缺陷V2C和单原子Al修饰空位缺陷V2C两个体系对H2气体分子的吸附能仅为-0.9851 eV、-2.7130 eV,均未能进一步改善V2C对H2气体分... 相似文献
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本文采用密度泛函理论方法,研究了氢气分子在硼取代富勒烯C19Bn+(n=0-3)表面的非解离吸附态、化学吸附态、及吸附态之间转换过渡态的结构和能量,得到了吸附态之间转换反应的势能面. 研究表明通过调整体系的离子化电荷可以调整吸附位点的电荷布居数,随着硼取代富勒烯离子化体系C19Bn+的吸氢活性位点电荷布居数增大,氢分子被极化的程度以及氢分子在材料表面的吸附能均逐渐增大,同时改变电荷布居数也对氢气分子在表面吸附态间转变势垒高度产生了量级为几个Kcal/mol的影响. 希望我们的研究能够对富勒烯储氢的进一步发展提供参考. 相似文献
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采用第一性原理方法研究了NH3分子在LiH(100)晶面的表面吸附情况.通过研究LiH(100)/NH3体系的吸附位置、吸附能和电子结构,发现NH3分子在LiH(100)晶面主要是化学吸附,初始位置为NH3分子中N-H键在Li顶住时失去一个H原子,并在LiH(100)面形成NH2基,其吸附能为0.511 eV,属于强化学吸附,吸附作用最强.此时NH2基与附近H原子和Li原子之间为离子键作用,NH2基中N—H键为共价键;NH3分子中另一个H原子与LiH表面的一个H原子形成一个H2分子逸出表面.H2分子中H-H键为明显的共价键. 相似文献
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采用第一性原理研究了H2O分子在Fe(100),Fe(110),Fe(111)三个高对称晶面上的表面吸附.结果表明,H2O分子在三个晶面上的最稳定结构皆为平行于基底表面的顶位吸附结构.H2O分子与三个晶面相互作用的吸附能及几何结构计算结果表明H2O分子与三个晶面的相互作用程度不同,H2O分子与Fe(111)晶面的相互作用最强,其次是Fe(100),相互作用最弱的是Fe(110)表面,而这与晶面原子
关键词:
第一性原理
Fe单晶表面
2O分子')" href="#">H2O分子
分子吸附 相似文献
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本文结合CALYPSO软件和密度泛函理论,详细研究了MB80/- (M=Li、Na、Rb、Cs)团簇的几何结构和成键特性。结构分析结果表明,MB80/- (M=Li、Na、Rb、Cs)团簇的基态结构都具有相似的几何构型,均为七棱锥状结构,并且随着掺杂原子的原子序数的增加,其M-B键的键长呈增加的趋势。通过稳定性分析,我们发现LiB8-团簇的HOMO-LOMO能隙以及结合能Eb最大,因此这个团簇是体系中相对稳定的结构。电荷转移分析表明,掺杂的碱金属原子在所研究体系中充当着电子供体的角色。最后,成键分析的结果显示,LiB8-团簇的稳定性来源于B原子的2p轨道以及Li原子的2s和2p轨道在HOMO和LUMO的高贡献;适应性自然密度划分分析显示, B和Li原子都参与了成键,这同样有利于LiB8-团簇的高稳定性的形成。希望我们的工作能为进一步研究碱金属掺杂硼团簇提供指导和帮助。 相似文献
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Using first-principles calculations, we systematically study the adsorption behavior of a single molecular H2O on the Be(0001) surface. We find that the favored molecular adsorption site is the top site with an adsorption energy of about 0.3 eV, together with the detailed electronic structure analysis, suggesting a weak binding strength of the H2O/Be(0001) surface. The adsorption interaction is mainly contributed by the overlapping between the s and pz states of the top-layer Be atom and the molecular orbitals 1b1 and 3a1 of H2O. The activation energy for H2O diffusion on the surface is about 0.3 eV. Meanwhile, our study indicates that no dissociation state exists for the H2O/Be(0001) surface. 相似文献
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The stability and the possible application of our recently reported SiC heterofullerenes inspire the investigation of their further stabilization through ion encapsulation. The endohedral complexes X@C12Si8, where X=Li+, Na+, K+, Be2+, Mg2+, Ca2+, Al3+, and Ga3+, are probed at the MPWB1K/6-311G? and B3LYP/6-311G* levels of theory. The optimized geometries show the expanding or contracting capability of C12Si8 in order to accommodate metal ion guests. The inclusion energies indicate the stability of the complexes compared to the components. Meanwhile, the calculated binding energies show the stabilization of C12Si8 through the inclusion of Be2+, Mg2+, Al3+, and Ga3+. The host-guest interaction that is probed through NBO atomic charges supports the obtained results. This study refers to “metal ion encapsulation” as a strategy for stabilization of SiC heterofullerenes. 相似文献
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Donglai Wang Haifeng Yu Xiaoping Sun Dongyan Hou 《Physica B: Condensed Matter》2011,406(6-7):1233-1237
The geometrical structures and electronic properties of six fullerene isomers of C100 were studied at the HF/6-31G? and B3LYP/6-31G? levels, respectively. The results of the fully optimized calculations show that three C100 isomers 449:D2, 425:C1 and 442:C2 are near isoenergetic isomers. The energies and properties of C100 hexaanions were calculated. The C1006? (450:D5) isomer is predicted to be the most stable isomer at the B3LYP/6-31G? level, and the C1006? (449:D2) isomer is 44.1 kcal/mol higher in energy. The heterofullerenes C96X4 (X=N, P, B, Si) formed from the initial C100 (449:D2) have also been investigated at the B3LYP/6-31G? level. The HOMO–LUMO gaps and aromaticities show that the replacement of fullerene carbon atoms with four heteroatoms can enhance the electronic stabilization of C100 (449:D2). 相似文献
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Using B3LYP/6-31G* density functional level of theory, the structural and optical properties of the C60 and M@C59X cages have been investigated. Results indicate that the charge on C atoms and band gap of C60 cage are changed dramatically with the substitution of one B or N atom at one of the C sites and the Li and Na atom encapsulations in the C60 cage. The Mulliken analyses show that the charge is transferred completely between the alkali atoms and the C59X cage. The substitutional and encapsulation doping (SED) reduce the optical gaps of the C60 cage. Also, the oscillator strengths of the absorption peaks are dependent on dopant types. 相似文献
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Adsorptions of SO2 on Al-, Ca-, Co-, Cu-, Ge-, Ni-, and Si-doped (8, 0) boron nitride nanotube (BNNT) have been studied using first-principles approach based on density functional theory in order to exploit their potential applications as SO2 gas sensors. The electronic properties of the BNNT-molecule adsorption adducts are strongly dependent on the dopants. The most stable adsorption geometries, adsorption energies, charge transfers, and density of states of these systems are thoroughly discussed. This work reveals that the sensitivity of (8, 0) BNNT based chemical gas sensors for SO2 can be drastically improved by introducing appropriate dopant. Si is found to be the best choice among all the dopants. 相似文献
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基于密度泛函理论的第一性原理计算方法,对Al_3X(X=Zr、Ti、Ce、Er)化合物生成焓、结合能、态密度、力学性能进行了计算.生成焓、结合能的计算结果表明:Al_3X(X=Zr、Ti、Ce、Er)化合物中,Al_3Zr最易形成,Al_3Ce则最难形成,计算所得的结合能均为负值,化合物具有热力学稳定性,其中Al_3Zr的热力学稳定性最好,Al_3Er则最差.态密度结果分析:Al_3X(X=Zr、Ti、Ce、Er)化合物在费米能级处态密度不为0,表现出金属特性,通过赝能隙大小判断出它们的共价性具有如下关系:Al_3ZrAl_3TiAl_3CeAl_3Er,这与Al-3s、3p电子分别与Zr-4d,Ti-3d,Ce-5d、4f,Er-4f轨道电子具有较为明显的轨道杂化作用有关.力学性能计算结果表明:Al_3Ti、Al_3Zr抵抗体积变形、剪切变形的能力、刚度较Al_3Er、Al_3Ce大.由于Al_3Zr、Al_3Ti、Al_3Ce、Al_3Er具有一定共价性,共价键为方向性键,不利于塑性变形,因此它们均表现为脆性材料. Al_3Zr、Al_3Ti、Al_3Ce、Al_3Er本征维氏硬度大小排序为:Al_3TiAl_3ZrAl_3ErAl_3Ce. 相似文献
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Using first-principles calculations based on density functional theory, we investigated systematically the electronic structures and magnetic properties of N monodoping and (Li, N) codoping in ZnO. The results indicate that monodoping of N in ZnO favors a spin-polarized state with a magnetic moment of 0.95 μB per supercell and the magnetic moment mainly comes from the unpaired 2p electrons of N and O atoms. In addition, it was found that monodoping of N in ZnO is a weak ferromagnet and it is the spin-polarized O atoms that mediate the ferromagnetic exchange interaction between the two N atoms. Interestingly, by Li substitutional doping at the cation site (LiZn), the ferromagnetic stability can be increased significantly and the formation energy can be evidently reduced for the defective system. Therefore, we think that the enhancement of ferromagnetic stability should be attributed to the accessorial holes and the lower formation energy induced by LiZn doping. 相似文献
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G.Y. Gao K.L. Yao M.H. SongZ.L. Liu 《Journal of magnetism and magnetic materials》2011,323(21):2652-2657
First-principles full-potential linearized augmented plane-wave method is used to investigate the electronic structure and magnetic properties of hypothetical zinc-blende and rocksalt LiS, NaS and KS. We find that all the compounds except rocksalt LiS exhibit half-metallic ferromagnetism with an integer magnetic moment of 1.00 μB per formula unit. The ferromagnetism results from the spin-polarization of p states of anion S. Total energies calculations indicate the rocksalt phase is lower in energy than the zinc-blende one. The total energy differences are about 0.38, 0.36 and 0.32 eV per formula unit for LiS, NaS and KS, respectively. Meanwhile, it is shown that rocksalt NaS and KS have the half-metallic gaps of 0.22 and 0.41 eV, respectively, and the half-metallic gaps are 0.03, 0.46 and 0.65 eV for zinc-blende LiS, NaS and KS, respectively. We also find the half-metallicity is robust against the lattice contraction up to 7% and 13% for rocksalt NaS and KS, respectively. Although rocksalt LiS is nonmagnetic and metallic at the equilibrium lattice constant, it shows half-metallic ferromagnetism when the lattice constant is larger than 5.40 Å. 相似文献