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1.
Ambrish Kumar Srivastava 《Molecular physics》2018,116(12):1642-1649
Benzene (C6H6) and polycyclic hydrocarbons such as naphthalene (C10H8), anthracene (C14H10) and coronene (C24H12) are well known aromatic organic compounds. We study the substitution of Li replacing all H-atoms in these hydrocarbons using density functional method. The vertical ionisation energy of such lithiated species, i.e. C6Li6, C10Li8, C14Li10 and C24Li12 ranges 4.24–4.50 eV, which is lower than the ionisation energy (IE) of Li atom. Thus, these species may behave as superalkalis due to their lower IE than alkali metal. However, these lithiated species possess planar and closed-shell structure, unlike typical superalkalis. Furthermore, all Li-substituted species are aromatic although their degree of aromaticity is reduced as compared to corresponding hydrocarbon analogues. We have further explored the structure of C6Li6 as star-like, unlike its inorganic analogue B3N3Li6, which appears as fan-like structure. We have also demonstrated that the interaction of C6Li6 with a superhalogen (such as BF4) is similar to that of a typical superalkali (such as OLi3). This may further suggest that the proposed lithiated species may form a new class of closed-shell organic superalkalis with aromaticity. 相似文献
2.
The glass formation in the SiO2-rich region of the ternary oxide system Al2O3–ZrO2–SiO2 with MgO, CaO, and TiO2 as melting aids was analyzed. The crystallization of glasses with different content of TiO2 and phase evolution with the temperature was studied by X-ray diffraction, infrared, laser Raman spectroscopy and transmission electron microscopy. The use of TiO2 favored formation and crystallization of the glasses due to the decrease of the viscosity of melts and acting as a nucleating agent. The crystalline phase of t-ZrO2 was developed at temperatures as low as 880°C whereas in as prepared specimens without TiO2 its presence was not detected. For the specimens with TiO2, t-ZrO2 and mullite were the principal phases at 1000°C. TiO2 addition did not change the crystallization sequence but decreased the formation temperature of the crystalline phases. Most of Ti4+ ions entered into t-ZrO2 and only a small portion in mullite, but the surplus was detected in ZrTiO4. 相似文献
3.
Chalcogenide glasses from the As2Se3-As2Te3-Sb2Te3 system were synthesized for the first time. The glass-forming region was determined by X-ray diffraction and electron microscopic analyses.The basic physicochemical parameters such as density (d), microhardness (HV) and temperatures of phase transformations (glass transition Tg, crystallization Tcr and melting Tm) were measured. Compactness and some thermomechanical characteristics such as volume (Vh) and formation energy (Eh) of micro-voids in the glassy network as well as the elasticity module (E) were calculated. The glass-forming ability was evaluated according to Hruby's criteria (KG). The correlation between composition and properties of the (As2Se3)x(As2Te3)y(Sb2Te3)z glasses was established and comprehensively discussed. 相似文献
4.
Julia Lyubina Oliver GutfleischMichael D. Kuz’min Manuel Richter 《Journal of magnetism and magnetic materials》2008
The structure and magnetic properties of LaFe13−xSix and Co-substituted LaFe11.8−xCoxSi1.2 alloys prepared by melt spinning, as well as of LaFe11.57Si1.43Hx hydrides prepared by reactive milling are investigated. The hysteresis in the temperature- and field-induced phase transitions is significantly reduced as compared with conventional bulk alloys, which makes these materials very attractive for magnetic refrigerant applications. The unusual combination of features characteristic of first- and second-order phase transitions in the La(Fe,Si)13-based compounds is discussed on the basis of density-functional electronic structure calculations. 相似文献
5.
Polycrystalline NiZn ferrites with the chemical formula (Ni0.3Zn0.7)1−xMexFe2O4 where Me is Cu with x=0.05, 0.1 and 0.25 have been prepared by a ceramic method. Certain magnetic properties such as the coercivity Hc, initial permeability μi and saturation magnetisation Ms of the ferrites have been measured and discussed from the point of view of the substituting element contents as well as the total pore volume. The Mössbauer spectra of selected samples have been analysed as well. According to the requirement of particular applications, the properties of NiZn ferrite have to be improved by means of proper substitution of selected ions. 相似文献
6.
Methods are described to determine the isotropic as well as the anisotropic part of the Knight shift from powdered samples of several V3X compounds (V3Co, V77.5Ni22.5, V3Rh, V3Pd, V3Pt and V3Ir). Measurements of the Knight shifts of the central line as well as the satellites prove to be necessary. The obtained values for Kiso are about 0.5% while Kax is not larger than 0.03%.The influence of the X elements on the quadrupolar interaction frequency vQ will be discussed. 相似文献
7.
Ailin Xia Chuangui JinDexin Du Guohui Zhu 《Journal of magnetism and magnetic materials》2011,323(12):1682-1685
We prepared NiZnCu ferrite powders with nominal composition Ni0.4−xZn0.6CuxFe2O4 (x=0-0.2) via chemical coprecipitation method with NaOH and Na2CO3 as coprecipitators. The structural and magnetic properties of these compounds were studied and compared. It is found that all the specimens exhibit single-phase structure after annealing. The saturation magnetization of specimens with NaOH as coprecipitator is lower than that with Na2CO3 as coprecipitator. It is also found that the growth of grains is hindered for specimens using Na2CO3 as coprecipitator. 相似文献
8.
Ambrish Kumar Srivastava 《Molecular physics》2014,112(21):2820-2826
In this work, a density functional survey on manganese oxyfluoride (MnOxFy) species for x + y = 1–4 is performed, in which an Mn atom interacts simultaneously with O as well as F atoms. The stabilities of all these species are established against dissociation to manganese oxides as well as fluorides and their relative stabilities are also discussed. It is revealed that the most favourable oxidation state of Mn is +4 in its oxyfluorides, same as in fluorides. For the first time, the superhalogen properties of MnOF3, MnO3F and MnO2F2 species are introduced on the basis of their high electron affinities as compared to halogens. The interaction of MnO2F2 superhalogen with an alkali metal (K) is considered via F atoms as well as O atoms which is similar to that in KF and leads to the formation of stable KMnO2F2 complex. Thus, this study is expected to motivate theorist to design a new series of superhalogen species using transition metals with mixed F and O ligands, as well as experimentalists to synthesise such novel complex compounds. 相似文献
9.
采用密度泛涵理论(density functional theory, DFT)中的广义梯度近似(generally gradient approximation, GGA)对富勒烯C72和内掺金属La富勒烯La2@C72三种同分异构体的几何结构和电子结构进行研究.发现在C72的三种同分异构体中,满足独立五边形规则(isolated-pentagon-rule,IPR)的C72(D6d<
关键词:
72')" href="#">C72
2@C72')" href="#">La2@C72
密度泛涵理论
几何结构
电子结构 相似文献
10.
The hot band system ν9 + ν11 ? ν11, ν10 + ν11 ? ν11 in allene-d4 was studied at a resolution near 0.010 cm?1. About 1500 partly overlapped hot band rotational lines were assigned and fitted to a model taking into account z-Coriolis resonance between the combination levels ν9 + ν11 and ν10 + ν11 as well as vibrational l-type resonances within these levels. Upperstate constants have been derived from an analysis in which the constants for the ν11 level were constrained. A detailed study of rotational as well as vibrational l-type doublings occurring in the KΔK = ?1 subband is presented, and the sign of vibrational l-type doubling constants for the ν10 + ν11 level is determined. A localized (x, y)-Coriolis resonance between ν10 + ν11 and ν4(B1) + ν11 is discussed and the interaction parameter is obtained as well as some constants for ν4 + ν11. 相似文献
11.
M.H. De Vasconcelos 《Physica A》1977,88(2):395-406
Using the optic-acoustic effect, measurements of the relaxation time were made after exciting the v4 mode of CD4. This was done for pure CD4 and for mixtures of CD4 with He, Ne, Ar and Kr, the results being 3.9±0.2, 1.8±0.2, 18±2, 70±15 and ? 100 μs at 1 atm, respectively. From the relaxation time dependence on mass as well as from a comparison between results for CH4 and CD4 it is concluded that energy transfer takes place via a vibration-rotation-translation (V-R-T) mechanism.Experiments were also conducted to study the most probable deexcitation path from the higher energy mode, v3, to translation. This was done for CD4-CD4 as well as for CD4-atom collisions. For pure CD4 deexcitation occurs via the lower energy group (v2, v4), while for CD4 mixtures it may also occur via the higher energy group (v1, 2v2, v2 + v4, 2v4). 相似文献
12.
Abstract The internal kinetics of NO2 as well as the kinetics of crossover between CH3F and NO3 were studied in mixtures of these polyatomics and rare gases. Subsequent to excitation of the CH3F to v 3=1 by the P(20) line of a 9.6μ Q-switch CO2 laser, fluorescence of NO2 at 6.12μ from v 3=1 was monitored. The equilibration rate of the stretching modes in NO2 was determined to be 46 ± 10 msec?1 torr?1 while the rate of stretches-bend equilibration was measured as 15 ± 3 msec?1 torr?1. The rate of crossover from excited CH3F to NO2 in high rare gas dilution was measured as 90 ± 20 msec?1 torr?1 and the reverse rate as 285 ± 60 msec?1 torr?1. Comparison to other triatomic systems as well as other experiments with mixtures of polyatomics are made and implications of laser “photochemistry” of NO2 reactions are discussed. 相似文献
13.
The C60 radical anion salts [P(C6H5)4]2C60X (X=Cl, Br, I) are grown via electrocrystallization and used as a model system to study the electron spin and nuclear spin dynamics as well as the molecular dynamics of C60 mono anions in the solid state, which obey universal laws. It is shown that [P(C6H5)4]2C60X is an exception among the fullerides, since the temperature dependence of the JT distortion, predicted for ionic C60, can be deduced. 相似文献
14.
《Solid State Ionics》2006,177(33-34):2851-2856
Thin films of BaCe0.8Gd0.2O3 were prepared by solid state reaction of two screen-printed layers over porous substrates. The first layer consists of the oxygen ion conductor Ce0.8Gd0.2O2 with a fluorite structure, whereas the top layer consists of BaCO3. After decomposition of the carbonate, BaO reacts with Ce0.8Gd0.2O2 forming the perovskite oxide BaCe0.8Gd0.2O3−δ with protonic conductivity. The in-situ reaction and densification on the porous substrates results in gastight thin layers of 10 to 50 μm and allows overcoming the problems due to the poor sinterability of the proton conductor. Two different porous substrates prepared by warm-pressing were studied as membrane supports, i.e., (i) porous composite NiO–Zr0.85Y0.15O2, commonly employed as solid oxide fuel cell anode and (ii) porous Ce0.8Gd0.2O2 oxide. The structural properties of the layer, compositional gradients and occurring phases are described, as well as water uptake, gastightness (He leaking rate) and emf measurement. Protonic conducting membranes are particularly suited not only for hydrogen separation combined with reforming and water–gas-shift converters but also as a protonic fuel cell electrolyte. 相似文献
15.
《Journal of Physics and Chemistry of Solids》2007,68(5-6):1087-1090
Phases of general formula M2FeV3O11, where M=Mg, Co, Ni and Zn as well as the orthorhombic modification of FeNb11O29, have been investigated by the help of IR and Mössbauer spectroscopy. It was found that the isostructural compounds Co2FeV3O11, Mg2FeV3O11, Zn2FeV3O11, as well as Ni2FeV3O11 with a different structure have one single and almost identical chemical environment for iron(III). The large Mössbauer quadrupole splitting measured suggests that iron(III) is located in a highly distorted octahedron. The IR spectra of three isostructural M2FeV3O11 compounds are similar but differ from that of Ni2FeV3O11. The Mössbauer spectrum of orthorhombic FeNb11O29 has been fitted with two doublets, their hyperfine parameters indicating iron in distorted octahedral environment. 相似文献
16.
两不同奇相干态组成的第种四态叠加多模叠加态光场的等阶N次方Y压缩 总被引:21,自引:4,他引:17
本文构造了由两不同奇相干态组成的第Ⅲ种四态叠加多模叠加态光场|Ψo(4),Ⅲ>q.利用新近建立的多模压缩态理论,详细研究了态|Ψo(4),Ⅲ>q的广义非线性等阶N次方Y压缩特性,结果发现由不呈现等阶高阶压缩效应的两奇相干态线性叠加组成的新量子光场态|Ψo(4),Ⅲ>q呈现出许多奇异物理现象:1)当压缩阶数N=4m(m=1,2,3,…,…)时,态|Ψo(4),Ⅲ>q始终恒处于等阶N-Y最小测不准态;2)当压缩阶数N=4m-2(m=1,2,3,…,…)时,在一定条件下,态|Ψo(4),Ⅲ>q的某一正交分量处于等阶N-Y最小测不准态时,另一正交分量则始终既不处于等阶N-Y最小测不准态,也不呈现等阶N次方Y压缩效应,这种现象称为“半相干态”效应;在另外一些条件下,态|Ψo(4),Ⅲ>q的两正交分量可分别呈现出等阶N次方Y压缩效应,其压缩特性具有周期性变化的、互补对称的关系.3)当压缩阶数N为奇数时,态|Ψo(4),Ⅲ>q始终不会呈现等阶N次方Y压缩效应,也不处于等阶N-Y最小测不准态,但在一定条件下可呈现“半相干态”效应. 相似文献
17.
The effect of transition element doping on the electronic and magnetic properties of La1.4Sr1.6Mn2O7
G.Q. Yu 《Solid State Communications》2007,141(3):136-140
The effect of transition element (TE=Cr, Fe, Co, Ni, Cu, Zn) doping on the electronic transport and magnetic properties in the bilayer manganite La1.4Sr1.6Mn2O7 is studied for the same dopant concentration fixed at 2%. Doping does not cause change in structure but different behavior in magnetic and transport properties. Except for Cr, all the other dopings significantly shift the magnetic transition temperature (TC) to a lower temperature. Associated with such a decrease, the insulator-metal transition temperature (TIM) decreases and the peak resistivity (ρp) at TIM increases. Cr doping enhances TC and TIM as well as decreases ρp. Fe doping apparently has a stronger effect than Co and Ni doping. It is also indicated that Cu doping causes an anomalously large increase in ρp. These behaviors are compared with those observed in other bilayer manganites such as La1.2Sr1.8Mn2O7 as well as in La0.7Ca0.3Mn1−xTExO3. 相似文献
18.
G. L. Messing S. Trolier-McKinstry E. M. Sabolsky C. Duran S. Kwon B. Brahmaroutu 《固体与材料科学评论》2004,29(2):45-96
Crystallographic texturing of polycrystalline ferroelectric ceramics offers a means of achieving significant enhancements in the piezoelectric response. Templated grain growth (TGG) enables the fabrication of textured ceramics with single crystal-like properties, as well as single crystals. In TGG, nucleation and growth of the desired crystal on aligned single crystal template particles results in an increased fraction of oriented material with heating. To facilitate alignment during forming, template particles must be anisometric in shape. To serve as the preferred sites for epitaxy and subsequent oriented growth of the matrix, the template particles need to be single crystal and chemically stable up to the growth temperature. Besides templating the growth process, the template particles may also serve as seed sites for phase formation of a reactive matrix. This process, referred to as Reactive TGG (RTGG), has been used to obtain highly oriented Pb(Mg1/3Nb2/3)O3-PbTiO3, Sr0.53Ba0.47Nb2O6, and (Na1/2Bi1/2)TiO3-BaTiO3. Highly oriented Bi4Ti3O12, Sr2Nb2O7, CaBi4Ti4O15, Pb(Mg1/3Nb2/3)O3-PbTiO3, Sr0.53Ba0.47Nb2O6 and (Na1/2Bi1/2)TiO3-BaTiO3 ceramics have been produced by TGG. The resulting ceramics show texture levels up to 90%, and significant enhancements in the piezoelectric properties relative to randomly oriented ceramics with comparable densities. For example, piezoelectric coefficients of textured piezoelectrics are from 2 to 3 times higher than polycrystalline ceramics and as high as 90% of the single crystal values. In textured PMN-PT, a low field (< 5 kV/cm) piezoelectric coefficient (d 33) of ~1600 pC/N was obtained with > 0.3% strain (at 50 kV/cm). The high field dielectric and electromechanical properties of textured perovskites are more hysteretic than those of single crystals, probably as a result of clamping by the residual template particles, residual random grains, the presence of non-ferroelectric second phases, and a wide orientation distribution. Lateral clamping of one grain by another may also be an important factor in fiber-textured samples. Means to further improve the quality of texture and thus properties of textured piezoelectric ceramics by TGG are presented. 相似文献
19.
Absorption spectra of CF2Cl2 were recorded around 923 cm–1, with a resolution of 50 MHz. The application of the molecular jet technique considerably simplifies the spectra as compared to room-temperature experiments. Rotational and vibrational temperatures were measured for CF2Cl2 pure and seeded in Ar or He. Molecular constants were obtained for thev
6 vibrational band of the two most abundant chlorine isotopic species, as well as vibrational band origines for thev
6±v
4 and thev
6±v
5 hot-bands of the CF2
35Cl2 isotope.Guest 相似文献
20.
《Current Applied Physics》2014,14(8):1140-1143
We stabilized SrRu0.9Fe0.1O3 single-crystalline films on SrTiO3 (001) and SrTiO3 (110) substrates using epitaxial strain during thin-film growth. X-ray diffraction (XRD) θ–2θ scans showed strong peaks demonstrating single-crystal quality. Fe doping in SrRuO3 had negative effects on the ferromagnetic properties, such as decreasing the Tc and saturated magnetic moment, as well as weakening the ferromagnetism. The negative effects were reduced when a suitable surface of the cubic substrate was selected for thin-film SrRuO3 growth. We found that the ferromagnetic properties, such as the Tc and saturated magnetic moment, differed depending on the substrate surface. The observed differences are discussed in terms of Ru–Ru nearest-neighbor distance. 相似文献