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A. N. Enyashin V. V. Ivanovskaya Yu. N. Makurin A. L. Ivanovskii 《Physics of the Solid State》2004,46(8):1569-1573
A comparative analysis of the stability factors and electronic structure of two possible crystalline forms of small fullerene C28 and endohedral fullerene Zn@C28 with diamond and lonsdaleite structures is performed using a cluster model. Atoms of elements that, when placed inside C28 cages, have no significant effect on the stability of free small-fullerene molecules are shown to be able to dramatically change the electronic properties and reactivity of the C28 skeleton and to be favorable for forming small-fullerene crystalline modifications, which are covalent crystals. In contrast, if the presence of foreign atoms inside C28 cages stabilizes the isolated nanoparticles, then molecular crystals (such as C60 fullerites) are formed due to weak van der Waals forces. 相似文献
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The atomic structure, charge and electronic parameters, and energies of formation of new “hybrid” nanostructures-nanopeapods Ti2@C80@C-NTs, regular linear ensembles of seven isomers of endohedral dititanofullerenes Ti2@C80 encapsulated into a carbon zigzag (19.0) nanotube—have been calculated by the self-consistent density functional tight-binding method (DFTB). The results are discussed in comparison to the “free” isomers of C80 fullerenes and Ti2@C80 endofullerenes, as well as to all-carbon nanopeapods, i.e., C80 isomers inside a carbon nanotube (C80@C-NT). It is demonstrated that the type of Ti2@C80 isomer determines the energy effect of its encapsulation into the tube (exo-or endothermic), the orientational arrangement of end-ofullerenes in the tube, the charge states of the Ti2@C80 and tube atoms, and the electronic properties of nanopeapods (semiconducting or metallic). 相似文献
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Tautomerism of Nunsubstituted benzohydroxamic acids and their anions in the gas phase was investigated by the semiempirical AM1 method. The possibility of estimating pK
a in aqueous solutions using calculated characteristics of molecules is demonstrated. 相似文献
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V. V. Ivanovskaya A. N. Enyashin A. L. Ivanovskii 《Journal of Structural Chemistry》2004,45(1):151-155
Quantum-chemical modeling of electronic structure and interatomic interaction parameters has been performed for a series of fullerenelike cage molecules based on the isoelectronic TiO2, SnO2, and SnS2. The above characteristics are analyzed in relation to the type of atomic configuration, as well as the size and chemical composition of a nanostructure. 相似文献
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The results of SCC-DFTB modeling of six known and hypothetical crystalline (3D) polymorphous modifications of boron nitride
(BN) are presented. Their comparative stability and structural, elastic, and electronic characteristics are analyzed on the
basis of the calculated data. 相似文献
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The results of molecular-dynamic modeling of the capillary filling of molybdenum disulfide MoS2 nanotubes with titanium tetrachloride molecules and the structure of the TiCl4 liquid inside the nanotubes are presented. 相似文献
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The electronic band structure and stability of extended nanocrystallites (NCs) of titanium monocarbide TiC were investigated by the electron density functional-tight binding (DFTB) technique. The stability of prismatic NCs increases with the number of atomic layers; the electronic spectrum of these compounds changes from semiconductor (for NC of minimal atomic size) to metallike type inherent in crystalline titanium carbide. 相似文献
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Bar-Sadan M Enyashin AN Gemming S Popovitz-Biro R Hong SY Prior Y Tenne R Seifert G 《The journal of physical chemistry. B》2006,110(50):25399-25410
MoS2 nanooctahedra are believed to be the smallest stable closed-cage structures of MoS2, i.e., the genuine inorganic fullerenes. Here a combination of experiments and density functional tight binding calculations with molecular dynamics annealing are used to elucidate the structures and electronic properties of octahedral MoS2 fullerenes. Through the use of these calculations MoS2 octahedra were found to be stable beyond nMo > 100 but with the loss of 12 sulfur atoms in the six corners. In contrast to bulk and nanotubular MoS2, which are semiconductors, the Fermi level of the nanooctahedra is situated within the band, thus making them metallic-like. A model is used for extending the calculations to much larger sizes. These model calculations show that, in agreement with experiment, the multiwall nanooctahedra are stable over a limited size range of 104-105 atoms, whereupon they are converted into multiwall MoS2 nanoparticles with a quasi-spherical shape. On the experimental side, targets of MoS2 and MoSe2 were laser-ablated and analyzed mostly through transmission electron microscopy. This analysis shows that, in qualitative agreement with the theoretical analysis, multilayer nanooctahedra of MoS2 with 1000-25 000 atoms (Mo + S) are stable. Furthermore, this and previous work show that beyond approximately 105 atoms fullerene-like structures with quasi-spherical forms and 30-100 layers become stable. Laser-ablated WS2 samples yielded much less faceted and sometimes spherically symmetric nanocages. 相似文献