共查询到20条相似文献,搜索用时 78 毫秒
1.
M.D. Ganji B. Abbaszadeh B. Ahaz 《Physica E: Low-dimensional Systems and Nanostructures》2011,44(1):290-297
We performed density functional theory calculations to investigate the possibility of formation of endohedrally H@(BN)n–fullerene (n: 24, 36, 60) and H@C60 complexes for potential applications in solid-state quantum-computers. Spin-polarized approach within the generalized gradient approximation with the Perdew–Burke–Ernzerhof functional was used for the total energies and structural relaxation calculations. The calculated binding energies show that H atom being incorporated into B60N60 nanocage can form most stable complexes while the B24N24 and C60 nanocages might form unstable complex with positive binding energy. We have also examined the penetration of an H atom into the respective nanocages and the calculated barrier energies indicate that the H atom prefers to penetrate into the B24N24 and B60N60 nanocages with barrier energy of about 0.47 eV (10.84 kcal/mol). Furthermore the binding characteristic is rationalized by analyzing the electronic structures. Our findings reveal that the B60N60 nanocage has fascinating potential application in future solid-state quantum-computers. 相似文献
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The X-ray emission SiKα1, 2 and SiKβ1 spectra of a series of phenylcyclosilanes (SiPh2) n (n = 4–6) have been obtained. Using the results of quantum-chemical calculations in the density functional theory approximation, the fine structure of SiKβ1 spectra has been interpreted. Distributions of densities of electron states of silicon atoms over the valence band have been constructed and the types of chemical bonds providing the Si-Si and Si-Ph interactions have been established. Based on the theory of natural bond orbitals, the chemical bonding in the studied series of phenylcyclosilanes has been analyzed. 相似文献
4.
运用密度泛函理论下的广义梯度近似和交换关联函数对Cu吸附(SiO2)n(n=1—8)团簇的几何结构、电荷分布、稳定性和电子性质进行了较详细的研究,结果表明: Cu原子易于和带有悬挂键的Si原子作用并形成"铜岛膜"; Cu吸附(SiO2)n团簇后Si原子失去电子能力减弱,O原子得到电子能力增强;Cu(SiO2)n(n
关键词:
密度泛函理论
2)n (n=1—8)团簇')" href="#">Cu(SiO2)n (n=1—8)团簇
近红外吸收 相似文献
5.
Using first-principles simulated annealing generalized gradient approximation density functional calculations based on norm-conserving pseudopotentials, we have investigated the geometric and electronic structures of low-energy silicon clusters (Sin, n=21–30). We have obtained new low-energy structures not reported previously. Our calculations suggest that the lowest energy structures are spherical ones including core atoms whose number increases with the cluster size. The trend of the binding energy as well as that of the energy difference between the highest occupied and the lowest unoccupied molecular orbitals is studied as a function of the cluster size and the number of core atoms. 相似文献
6.
The HeI and NeI photoelectron spectra of irontricarboniyl complexes with cyclic diene ligands—αmethylstyrene, orthoquinodimethane, and cyclooctatetraene—were obtained. The results of quantum-chemical calculations of the molecules of these compounds in the approximation of the density functional theory (B3LYP/6-31G*) are presented. It is shown that this approximation describes well the excited ionic states of the π complexes under study. The relative ionization cross sections σπ and σ3d , which characterize the probability of removal of electrons from the molecular π-ligand and 3d-metal orbitals, are estimated. The mechanism of the selective coordination of the Fe(CO)3 groups to corresponding organic ligands is discussed. The energies of the L-Fe(CO)3 chemical bond are calculated. 相似文献
7.
M. Moakafi R. Khenata A. Bouhemadou H. Khachai B. Amrani D. Rached M. Rérat 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(1):35-42
We report results of first-principles calculations for the electronic and optical properties under pressure effect of Li2O, Na2O, Ki2O and Rb2O compounds in the cubic antifluorite structure, using a full relativistic version of the full-potential augmented plane-wave
plus local orbitals (FP-APW+lo) method based on density functional theory, within the local density approximation (LDA) and
the generalized gradient approximation (GGA). Moreover, the alternative form of GGA proposed by Engel and Vosko (GGA-EV) is
also used for band structure calculations. The calculated equilibrium lattices and bulk moduli are in good agreement with
the available data. Band structure, density of states, and pressure coefficients of the fundamental energy gap are given.
The critical point structure of the frequency dependent complex dielectric function is also calculated and analyzed to identify
the optical transitions. The pressure dependence of the static optical dielectric constant is also investigated. 相似文献
8.
Electronic, optical and thermoelectric parameters of the Ti2N:Mn graphene sheet have been calculated by the density functional theory (DFT) framework. Our calculations were performed with full potential linear augmented plane waves plus local orbitals (FP-LAPW + lo) method and the exchange correlation potential was approximated by generalized gradient approximation (GGA). The Ti2N:Mn graphene sheet has anisotropic electronic behaviors indicating the magnetic property. The group velocity and effective mass in the valance band maximum (VBM) and conduction band minimum (CBM) have the high and low amounts, respectively. The optical response to the incident light in the infrared, visible area and ultraviolet edge are completely asymmetric while the optical responses at x and z directions are metallic and semiconductor, respectively. Thermoelectric parameters of Ti2N:Mn graphene have sensitivity to the external magnetic field, and the Seebeck (S) and merit coefficients (ZT) at spin up have great amounts in 150 K. 相似文献
9.
Based on the density functional theory(DFT),the electronic structures and optical properties of Mg2Pb are calculated by using the local density approximation(LDA)and plane wave pseudo-potential method.The calculation results show that the indirect band gap width of Mg2Pb is 0.02796 eV.The optical properties of Mg2Pb have isotropic characteristics,the static dielectric function of Mg2Pb is1(0)=10.33 and the refractive index is n0=3.5075.The maximum absorption coefficient is 4.8060×105cm 1.The absorption in the photon energy range of 25–40 eV approaches to zero,shows the optical colorless and transparent behaviors. 相似文献
10.
Ali Sebetci 《Journal of magnetism and magnetic materials》2012,324(4):588-594
The structural, energetic, electronic and magnetic properties of small bimetallic ConPtm (n+m≤5) nanoalloy clusters are investigated by density functional theory within the generalized gradient approximation. A plausible candidate for the ground state isomer and the other possible local minima, binding energies, relative stabilities, magnetic moments, the highest occupied and the lowest unoccupied molecular orbital energy gaps have been calculated. It is found as a general trend that average binding energies of Co-Pt bimetallic clusters increase with Pt doping. Planar structures of pure Co clusters become 3D with the addition of Pt atoms. CoPt2, Co2Pt2, Co3Pt2, and CoPt4 nanoalloys are identified as the most stable species since they have higher second finite difference in energy than the others. Pt doping decreases the total spin magnetic moment gradually. A rule for the prediction of the total spin moments of small Co-Pt bimetallic clusters is derived. 相似文献
11.
Patrick O'Keeffe Paola Bolognesi Anna Rita Casavola Daniele Catone Nicola Zema Stefano Turchini 《Molecular physics》2013,111(19):2025-2037
The electronic structures of pyrimidine and a selection of its halogen-substituted derivatives have been investigated using ultraviolet photoelectron spectroscopy and ab initio quantum chemical methods. Assignments are proposed for all of the features in the PES spectra by comparison with the vertical ionization energies of the molecular orbitals calculated using the partial third-order quasiparticle approximation as applied to electron propagator theory and a corrected density functional method based on the B3LYP functional. The shifts of the outermost five molecular orbitals of the pyrimidine ring structure in the halogen-substituted derivatives with respect to the binding energies of the equivalent orbitals in the parent pyrimidine molecule are discussed as a function of the identity and ring position of the halogen atom. 相似文献
12.
The bandgap and band bowing parameter of semiconductor alloys are calculated with a fast and realistic approach. The method is a dielectric scaling approximation that is based on a scissor approximation. It adds an energy shift to the bandgap provided by the local density approximation (LDA) of the density functional theory (DFT). The energy shift consists of a material-independent constant weighted by the inverse of the high-frequency dielectric constant. The salient feature of the approach is the fast calculation of the dielectric constant of alloys via the Green function (GF) of the TB-LMTOs (tight-binding linear muffin-tin orbitals) in the atomic sphere approximation (ASA). When it is applied to highly mismatched semiconductor alloys (HMAs) like Zn TexSe1?x, this method provides a band bowing parameter that is different from the band bowing parameter calculated with the LDA due to the bowing exhibited also by the high-frequency dielectric constant. 相似文献
13.
《Chinese Journal of Physics (Taipei)》2018,56(4):1756-1763
First-principles full-potential linearized augmented plane-wave method based on density functional theory is used to investigate the structural, electronic and optical properties of the cubic fluoroelpasolites Cs2NaYF6 within the local density approximation (LDA) and generalized gradient approximation (GGA) for potential exchange correlation. The modified Becke–Johnson (mBJ) potential approximation is also used for calculating the electronic and optical properties of the material. We have analyzed the structural parameters, total and partial densities of states, dielectric functions, absorption and reflectivity. The results show that the band structure of the fluoroelpasolites Cs2NaYF6 has an insulating behavior for the two directions of spin and as a result there is no net magnetic moment. A wide band gap of 9.6 eV is obtained with mBJ-GGA, which allows the application of this material as X-ray storage phosphor materials and scintillators. 相似文献
14.
We determine the structural, electronic, elastic and optical properties of fluoro-perovskite KZnF3 using the full potential linear augmented plane wave approach (FP-LAPW) based on the density functional theory (DFT). The exchange-correlation potential is treated by the local density approximation (LDA) and the generalized gradient approximation (GGA). The calculated structural parameters are in good agreement with the available data. We have obtained an indirect band gap. The effect of the pressure on the band gaps is investigated. We evaluate the elastic constants (Cij), elastic moduli and the Debye temperature. The imaginary and the real parts of the dielectric function ε(ω) and some optical constants are also calculated. 相似文献
15.
Electronic and optical properties of Sr(Ti,Zr)O3 crystals in the cubic (Pm-3m) and tetragonal (I4/mcm) phase were calculated by the first-principles calculations using the density functional theory and the local density approximation. The band structure of cubic and tetragonal phases show an indirect band gap at (R-Γ) point and at (M-Γ) point in the Brillouin zone, respectively. The linear photon-energy dependent dielectric functions and some optical properties such as the absorption coefficient, energy-loss function and reflectivity are calculated for both phases. The optical properties of tetragonal phase of Sr(Ti,Zr)O3 were investigated by theoretical methods for the first time. We have also made some comparisons with the available related experimental and theoretical data. 相似文献
16.
The structural, energy, and optical properties of charged and neutral molecular clusters (MCs) of silver Agn (n = 2–5) have been simulated within the density functional theory (DFT). It has been shown that the electronic absorption spectrum of neutral MCs is shifted toward lower energies compared to the charged ones. The strengths of the oscillators of neutral MCs are mainly larger than the ones of charged MCs. A comparison of the simulation results with the previously obtained experimental ones for glasses with silver MCs has been carried out. 相似文献
17.
Rajendra K. Shivade Brahmananda Chakraborty 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(9):198
Boron nano-clusters of various shapes and sizes have potential applications asscintillating detector and hydrogen storage material. Using time dependent densityfunctional theory (TDDFT) as implemented in CASIDA we have studied the linear opticalabsorption spectra for boron clusters Bn (n = 2–5) and compared withpreviously reported results using Hatree-Fock (H-F) based method where the spectrum islimited to 8 eV due to exclusion of excitation into very high energy unoccupied orbital.The optical spectra fall in the visible and near UV region and are very much dependent onthe shape of the isomer. We have obtained additional peaks for B2 linear, B3 triangular, B4 rhombus and square shapedisomers beyond 8 eV which were missing in the previous H-F based study and hassignificance as they fall below the ionization potential. We correlate the opticalspectrum with the shape of the Kohn-Sham orbitals and HUMO-LUMO gap and assess comparativestability of various Bn (n = 2–5) clusters in termsof HUMO-LUMO gap, bond-length and relative energy. TDDFT computed optical spectroscopycorrelated with Kohn-Sham orbitals and HUMO-LUMO gap and its comparison with H-F basedmethod may give significant knowledge regarding geometry and optical properties ofBn (n = 2–5) clusters enablingto distingush between various isomers of Bn clusters. 相似文献
18.
The electronic and geometrical structures of neutral and charged YOn (n=2–12) clusters have been investigated using density functional theory (DFT) with generalized gradient approximation. The oxygen atom in YOn has been found to be in oxo, peroxo and in superoxo forms. The geometrical structures and topologies of small size anionic clusters resemble that of neutral clusters. Yttrium showed higher coordination number than scandium. Computed results reveal the existence of YO10 cluster to have a penta-peroxo oxygen with a homoleptic Y(η2 –O2)5 geometrical configuration. The HOMO–LUMO gaps decrease with increasing n due to the increase in 2p orbital population of oxygen atoms. It has been shown that in these clusters bonding are predominantly ionic in nature and anions are thermodynamically more stable, due to the charge delocalization between the metal atom and oxygen ligands. YO10+ and YO12+ were found to be highly exothermic to release one and two oxygen molecules, while YO11+ dissociates though the ozonide dissociation channel. Computed absorption spectra of small clusters are mainly contributed by yttrium metal d and s valence orbitals. The absorbance spectra, shifts towards lower energy with cluster size increase, while charge has no substantial effect on the absorption spectrum. 相似文献
19.
V. I. Vovna V. V. Korochentsev A. A. Komissarov I. B. L’vov 《Russian Journal of Physical Chemistry B, Focus on Physics》2013,7(3):220-224
Density functional theory and photoelectron spectroscopy are used to study the electronic structure of nickel acetylacetonate Ni(acac)2. Based on the calculated energies and composition of the molecular orbitals and the pattern of localization of the electron density, the nature of the gas-phase photoelectron spectrum bands of Ni(acac)2 is examined, and a new interpretation of it is proposed. The energies of the Kohn-Sham orbitals are assigned to the experimental vertical ionization energies in the approximation of the extended Koopmans theorem, which enables, with consideration given to the dependence of the Koopmans defect on the nature of the electronic level, to obtain a good agreement between the calculated orbital energies and experimental data on ionization energies. 相似文献
20.
A first principles calculation is carried out on a typical heavy fermion system-CeCu2Si2 by using a many-body method combing density functional theory (DFT) and dynamical mean-field theory (DMFT) along with the on-site Coulomb repulsion (represented by the Hubbard U parameter) for capturing the electronic correlation due to the incompletely filled Ce 4f orbitals. The results establish that the average occupation of Ce 4f electrons nf is about 1.02 (mainly 4f1 atomic configuration), close to the nominal occupation in pure Ce metal and in good agreement with the spectrum function in this work and the available experimental observations. The imaginary part of the impurity Green function indicates that the Ce 4f j = 5/2 and j = 7/2 states have metallic and insulating behavior, respectively. The dehybridization between the Ce 4f orbitals and ligand valence orbitals in the vicinity of the Fermi level is responsible for the localized 4f state and heavy fermionic behavior in this system. 相似文献