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We have studied the adsorption of water molecules on the inner and outer surfaces of nanotubes generated by rolling (001) layers of SrTiO3 cubic crystals. The stability and the atomic and electronic structures of the adsorbed layers are determined by using hybrid density functional theory. The absorption energy and the preferred adsorbate structure are essentially governed by the nature of the surface of the nanotube. Dissociative adsorption prevails on the outer nanotube surfaces. The stability of the adsorbed layers on the inner surfaces is related to the possibility of the formation of hydrogen bonds between water molecules and surface oxygen atoms, and depends on the surface curvature. The presence of water molecules on the inner surface of the nanotubes leads to an increase of the electronic band gap. Externally TiO2‐terminated nanotubes could be used for the photocatalytic decomposition of water by ultraviolet radiation.  相似文献   
2.
Physics of the Solid State - A force field is proposed that reproduces with a high accuracy a large number of properties of the bulk crystal MoS2 phases, monolayers, and nanotubes. The reproduced...  相似文献   
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First-principles calculations have been used to study the atomic structure, preferred sites and adsorption energies for water adsorption at different terminations of the cubic phase of perovskite-structured BaHfO3 and BaZrO3. By considering different initial positions of water molecules, the possibility of water dissociation has been investigated. It is demonstrated that the site selectivity and the form of adsorbed molecule can be affected by the choice of surface unit cell. Dissociative adsorption was found to be favorable for all surfaces in consideration. Hydroxylation of ZrO2- and HfO2-terminated surfaces is accomplished by a noticeable reconstruction of the surface structure of cubic phase towards the orthorhombic phase. Calculated atomic charges in bare and hydroxylated surfaces show that BaHfO3 crystal is slightly more ionic than BaZrO3.  相似文献   
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The first‐principles calculations using hybrid exchange‐correlation functional and localized atomic basis set are performed for BaTiO3 (BTO) nanolayers and nanotubes (NTs) with the structure optimization. Both the cubic and the ferroelectric BTO phases are used for the nanolayers and NTs modeling. It follows from the calculations that nanolayers of the different ferroelectric BTO phases have the practically identical surface energies and are more stable than nanolayers of the cubic phase. Thin nanosheets composed of three or more dense layers of (0 1 0) and (0 1 ) faces preserve the ferroelectric displacements inherent to the initial bulk phase. The structure and stability of BTO single‐wall NTs depends on the original bulk crystal phase and a wall thickness. The majority of the considered NTs with the low formation and strain energies has the mirror plane perpendicular to the tube axis and therefore cannot exhibit ferroelectricity. The NTs folded from (0 1 ) layers may show antiferroelectric arrangement of Ti? O bonds. Comparison of stability of the BTO‐based and SrTiO3‐based NTs shows that the former are more stable than the latter. © 2012 Wiley Periodicals, Inc.  相似文献   
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