共查询到20条相似文献,搜索用时 10 毫秒
1.
Metal doped ZnO nanostructures have attracted extensive attention as chemical sensors for toxic gases. An experimental study has previously shown that Ga-doped ZnO nanostructures significantly show a higher electronic response than the undoped sample toward CO gas. Here, the electronic sensitivity of pristine and Ga-doped ZnO nanoclusters to CO gas is explored using density functional theory computations (at B3LYP, PBE, M06-2X, and ωB97XD levels). Our results reproduce and clarify the electrical behavior which has been observed experimentally from the ZnO nanoparticles after the exposure to CO gas. We showed that the calculated change of HOMO-LUMO gap may be a proper index for the change of electrical conductance which is measurable experimentally. It was found that, in contrast to the pristine ZnO nanocluster, the electronic properties of Ga-doped cluster are sharply sensitive to the presence of CO gas which is in good accordance with the results of the experimental study. 相似文献
2.
The electronic and adsorption properties of the pristine, Al-, Ga-, and Ge-doped BN nanotubes interacted with 5-fluorouracil molecule (5-FU) were theoretically investigated in the gas phase using the B3LYP density functional theory (DFT) calculations. It was found that the adsorption behavior of 5FU molecule on the pristine (8, 0) and (5, 5) BNNTs are electrostatic in nature. In contrast, the 5FU molecule (O-side) implies strong adsorption on the metal-doped BNNTs. Our results indicate that the Ga-doped presents high sensitivity and strong adsorption with the 5-FU molecule than the Al- and Ge-doped BNNTs. Therefore, it can be introduced as a carrier for drug delivery applications. 相似文献
3.
Chikashi Suzuki Tsuyoshi Nishi Masami Nakada Tomohito Tsuru Mitsuo Akabori Masaru Hirata Yoshiyuki Kaji 《Journal of Physics and Chemistry of Solids》2013
We investigated the electronic state of an (Am,U) mixed oxide with the fluorite structure using the all-electron full potential linear augmented plane wave method and compared it with those of Am2O3, AmO2, UO2, and La0.5U0.5O2. The valence of Am in the mixed oxide was close to that of Am2O3 and the valence of U in the mixed oxide was pentavalent. The electronic structure of AmO2 was different from that of Am2O3, particularly just above the Fermi level. In addition, the electronic states of Am and U in the mixed oxide were similar to those of trivalent Am and pentavalent U oxides. These electronic states reflected the high oxygen potential of AmO2 and the heightened oxygen potential resulting from the addition of Am to UO2 and also suggested the occurrence of charge transfer from Am to U in the solid solution process. 相似文献
4.
Ram Manohar Yadav Dinesh Pratap Singh T. Shripathi O. N. Srivastava 《Journal of nanoparticle research》2008,10(8):1349-1354
We report the observations made on the synthesis and characterization of C–N nanotube blocks and Y-junctions in bamboo-like
C–N nanotubes. The C–N nanotube Blocks have been synthesized by pyrolyzing the mixture of silver nitrate acetonitrile solution
and ferrocene benzene solution. The structural/microstructural characterization of the as-synthesized material has been done
using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray photoelectron spectroscopic (XPS)
analysis has been carried out to confirm the presence of nitrogen in nanotubes. These investigations reveal the formation
of blocks of bamboo-like nanotubes having the dimension 300 × 200 × 30 μm and the diameter is 20–50 nm. We also observe the
formation of Y-junctions in bamboo-like nanotubes as we spray the acetonitrile ferrocene and AgNO3 mixture. The length of the synthesized Y-junction nanotube bundles is ~2 μm. Some more complex Ψ-shaped junctions are also
found to be present. The diameters of the Y-junction nanotubes is ~80 nm at the junction and 25–50 nm at the branches. 相似文献
5.
We have studied the electronic structure and optical responses of 3-nitroaniline and 4-nitroaniline crystals within the framework of density functional theory (DFT). In addition, the excitonic effects are investigated by using the recently published bootstrap exchange-correlation kernel within the time dependent density functional theory (TDDFT) framework. Our calculations based on mBJ approximation yield the indirect band gap for both crystals, but the larger one for m-NA. Due to the excitonic effects, the TDDFT calculations gives rise to the enhanced and red-shifted spectra (compared to RPA). Due to the weak intermolecular interactions, band-structure calculations yield bands with low dispersion for both crystals. This study shows that the substituent groups play an important role in the top of valence band and the bottom of conduction band. Due to the linear structure of p-NA molecule, the highest peaks are located in the optical spectra of p-NA crystal, while m-NA has more sharp peaks, especially at lower energies. Both DFT and TDDFT calculations for the energy loss spectra show plasmon peaks around 27 and 28 eV for p-NA and m-NA, respectively. Due to the non-centrosymmetric structure of m-NA crystal, we also have reported its nonlinear spectra and the 2ω/ω intra-band and inter-band contributions to the dominant susceptibilities. Findings indicate the opposite signs for these contributions, especially at higher energies. The comparison between nonlinear spectra and the linear spectra (as a function of both ω and 2ω) reveals the significant resemblance between linear and nonlinear patterns. In addition to the reasonable agreement between our results with experimental data, this study reveals the spectral similarities between crystalline susceptibility and molecular polarizability. 相似文献
6.
Ab Initio Study on Structural and Magnetic Properties of Ni-Pd and Ni-Pt Linear and Zigzag Nanowires
Employing the accurate frozen-core full-potential projector augmented-wave method, the self-consistent electronic structure calculations were carried out on pure Ni, Pd, Pt and mixed Ni-Pd and Ni-Pt free-standing linear and zigzag nanowires. The bond lengths for all these systems are generally increased as their structures change from the linear to the zigzag chain. The bond lengths for Ni-Pd and Ni-Pt wires are in between the values of corresponding pure system and the bond angles around 60° suggesting the possible formation of Ni-Pd and Ni-Pt bimetallic materials. In mixed Ni-Pd and Ni-Pt chains, the Ni, Pd, and Pt atoms have quite high local magnetic moments. The calculations suggest that the magnetic moments in linear nanowires are generally larger than the ones of corresponding zigzag nanowires. It is found that there is hybridization between Ni 3d and Pd 4d, Ni 3d and Pt 5d states, which may significantly affect structural stability and magnetism of Ni-Pd and Ni-Pt nanowires. 相似文献
7.
Using the DFT-B3LYP calculations we investigate the adsorption of Li atom on CNT, BNNT, AlNNT and SiCNT. We found that Li atom can be chemisorbed on zig-zag SiCNT with binding energy of −2.358 eV and charge transfer of 0.842 |e|, which are larger than the results of other nanotubes. The binding energy of Li on SiCNT is foun to be stronger than activation energy barrier indicating that Li metal could be well dispersed on SiCNTs. Furthermore, the average voltage caused by the lithium adsorption on SiCNT demonstrated that SiCNTs could exhibit as a stable anode similar to the lithium metal anode. The binding nature has been rationalized by analyzing the electronic structures. Our findings demonstrate that Li-BNNT, Li-SiCNT and Li-AlNNT systems exhibit spin polarized behaviors and can fascinating potential application in future spintronics. Also, Li-SiCNT system with rather small band gap might be a promising material for optical applications and active molecule in its environment. 相似文献
8.
For the solid-state density functional program Elk a module was developed that enables to interface the crystal orbitals data into the DGrid package. Within DGrid the real-space electronic properties, like the electron density and its gradient or Laplacian, kinetic energy density, electron localizability indicator, etc., are computed. The properties can be searched for critical points as well as for the interconnection lines between them. Additionally, the basins can be evaluated and the property integrals can be calculated. The results of topological analysis for fcc Al, MgB2, CaTiO3, and urea molecular crystal are discussed and compared with the experimental data. The role of certain computation parameters of (L)APW method is also analyzed. 相似文献
9.
In order to find a novel sensor, reactivity and sensitivity of the intrinsic, Al- and Si-doped BC3 graphene-like sheets to an acetone molecule were investigated by using B3LYP and ωB97X-D density functional calculations. Adsorption of acetone on the intrinsic, Al- and Si-doped BC3 sheets releases energies of about 7.2, 36.5 and 24.8 kcal/mol, respectively, using ωB97X-D. The Si-doped sheet presents high sensitivity to acetone compared with the intrinsic and Al-doped sheets indicated by the calculated geometrical structures and electronic properties for these systems. The HOMO/LUMO energy gap of Si-doped BC3 sheet is significantly decreased from 2.20 to 1.65 eV (B3LYP), which would result in electrical conductance increment. Thus, Si-doped sheet are expected to be a potential candidate for detecting the presence of acetone. 相似文献
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12.
S. H. Ma X. T. Zu Z. Y. Jiao H. Y. Xiao 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(3):319-324
Extended density functional theory calculations with the spin interpolation formula of Vosko, Wilk, and Nusair (VWN) are
employed to study the effect of atomic S adsorption on Co(0001) surface. Besides the site preference for atom S in fcc-hollow
site and adsorption geometry structures are in good agreement with experiments and previous calculations, some differences
are also reported for the geometry of S in hcp-hollow site. Moreover, vibrational frequency, magnetic moments and electronic
structure analysis are presented in more detail. 相似文献
13.
《Physics letters. A》2014,378(30-31):2184-2190
The electronic sensitivity of pristine, Ni- and Si-doped graphynes to ammonia (NH3) molecule was investigated using density functional theory, including dispersion correction. It was found that NH3 is weakly adsorbed on the sheet, releasing energy of 2.9–4.4 kcal/mol, and the electronic properties of the sheet are not significantly changed. Although both Ni-doping and Si-doping make the sheet more reactive and sensitive to NH3, Si-doping seems to be a better strategy to manufacture NH3 chemical sensors because of higher sensitivity. Our calculations show that the HOMO/LUMO gap of the Si-doped sheet is significantly decreased from 2.13 to 1.46 eV after the adsorption of NH3, which may increase the electrical conductance of the sheet. Therefore, the doped sheet might convert the presence of NH3 molecules to electrical signals. Moreover, the shorter recovery time of the Si-doped sheet is because of the middle adsorption energy of 39.3 kcal/mol in comparison with 55.1 kcal/mol for the Ni-doped sheet. 相似文献
14.
The article presents a combined theoretical and experimental study attempting to show how Pd nanoparticles (NPs) loading onto SnO2 substrate improves the acetone gas sensing performance. Pristine nanostructured SnO2 and Pd nanoparticles (Pd NPs) loaded SnO2 substrates have been prepared, characterized, and their acetone sensing performances have been measured. Experimental measurements have shown that Pd NP loading onto SnO2 suppresses the interfering effects of ethanol, water vapors, etc., and enhances the acetone sensor response, reversibility, response/recovery speeds, and signal-to-noise ratio. Various parameters like the adsorption energy, HOMO–LUMO energy gap, charge distribution, polarizability change, electrophilicity index, global hardness, etc., of several model systems, have been computed by using DFT. The computed parameters have been correlated with the conductivity, local reactivity, sensor response and selectivity, response/recovery times, etc., of the systems to understand the molecular-level effects of the Pd NP loading onto the SnO2 on the gas sensing process. 相似文献
15.
我们将芳香性扩展到全金属阴离子团簇La42-.运用从头算方法(B3LYP/LANL2DZ, B3PW91/LANL2DZ and MP2/LANL2DZ)进行了结构优化.计算结果显示,阴离子团簇有两个同分异构体,一个是C2v结构,另一个是正方形D4h结构.进一步对能量的分析得出,D4h结构比C2v结构更稳定.对最稳定的D4h结构计算了核独立位移(NICS),结果显示正方形的La42-环呈现强芳香性.详细的分子轨道(Mos)分析揭示正方形的La42-环拥有四个独立的离域化成键系统,每一个系统拥有两个电子,分别满足4n + 2芳香性电子计算规则,因此呈现四重芳香性. 相似文献
16.
我们将芳香性扩展到全金属阴离子团簇La2-4.运用从头算方法(B3LYP/LANL2DZ,B3PW91/LANL2DZ and MP2/LANL2DZ)进行了结构优化.计算结果显示,阴离子团簇有两个同分异构体,一个是C2v结构,另一个是正方形D4h结构.进一步对能量的分析得出,D4h结构比C2v结构更稳定.对最稳定的D4h结构计算了核独立位移(NICS),结果显示正方形的La2-4环呈现强芳香性.详细的分子轨道(Mos)分析揭示正方形的La2-4环拥有四个独立的离域化成键系统,每一个系统拥有两个电子,分别满足4n+2芳香性电子计算规则,因此呈现四重芳香性. 相似文献
17.
M. P. Housden 《Molecular physics》2013,111(17-18):2353-2361
The binding of the noble gas dimers is examined using a theory in which the Hartree–Fock interaction energy is augmented with both a short-range correlation term derived from the theory of a uniform electron-gas plus a dispersion energy damped according to the theory of Jabobi and Csanak. The good agreement between the predicted and experimental binding energies and equilibrium inter-nuclear separations confirms that this approach captures the essential physics of the interaction. A review of other methods confirms the previously reported failures of density functional theory. A further survey shows that fully ab initio variational methods must be taken to the very refined level of coupled cluster theory with a large quadruple or quintuple zeta basis set if they are to achieve greater accuracy than the approach presented here. 相似文献
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The first principles within the full potential linearized augmented plane wave (FP-LAPW) method was applied to study the structural and electronic properties of cubic perovskite-type compounds BiAlO3 and BiGaO3. The lattice constant, bulk modulus, its pressure derivative, band structure and density of states were obtained. The results show that BiGaO3 should exhibit higher hardness and stiffness than BiAlO3. The Al–O or Ga–O bonds are typically covalent with a strong hybridizations as well as Bi–O ones that have a significant ionic character. Both materials are weakly ionic and exhibit wide and indirect band gaps, which are typical of insulators. 相似文献
20.
Density functional theory (DFT) and density functional perturbation theory (DFPT) calculations were used to investigate the vibrational and thermodynamic properties of orthorhombic stannate CaSnO3 compound. Our approach was based on the generalized gradient approximation with dispersion correction (GGA+D), considering the norm-conserved pseudopotentials. The phonon dispersion relation as well as theoretical peaks of the infrared (IR) and Raman spectrum in the frequency range of 100–800 cm−1 was analyzed and assigned. The thermodynamic potentials and the specific heat at constant volume of the CaSnO3 compound are also calculated, whose dependence with the temperature are discussed. 相似文献