Home  About us  Contact
 

Crystal Facets (crystal + facet)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

Spontaneous segregation on a hybrid chiral surface

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2008
Szabelski
Abstract Segregation of enantiomers in two-dimensional adsorbed layers is a process that is usually controlled by anisotropic directional interactions between adsorbed molecules. In this contribution, we propose a simple theoretical model in which the chiral segregation occurs even though the lateral interactions are neglected. In particular, we consider a solid surface composed of two domains with different patterns of active sites being mirror images of each other. The domains of opposite handedness represent crystal facets of a composite chiral material which are adjoined to form a heterochiral adsorbing surface. To explore equilibrium properties of the system, we use Canonical Ensemble Monte Carlo method for a square lattice. The influence of factors such as energetic properties of the surface and density of the adsorbed layer on the extent of separation is examined. The obtained results indicate that effective two-dimensional separation on the hybrid chiral surface assumed in our model can be achieved only at sufficiently low adsorbate densities. The results also suggest that the segregation on the hybrid surface would be a promising method of enantiodiscrimination for those chiral molecules which do not exhibit strong lateral interactions. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008 [source]

Relationship Between Geometric Structures of Catalyst Particles and Growth of Carbon Nanocoils,

CHEMICAL VAPOR DEPOSITION, Issue 4-6 2010
Da-Wei Li
Abstract The relationship between the geometric structures of catalyst particles and the growth of carbon nanocoils (CNCs) is investigated. It is found that the CNCs usually consist of over two, but less than five tubules. The catalyst particles at the tips of CNCs are all polyhedron structures, in most cases, hexahedron. It is considered that a catalyst particle has two kinds of crystal facets, the catalytically active facet and the carbon precipitation facet. The active facet mainly plays the roles of decomposition of hydrocarbon and diffusion of the formed carbon atoms, while carbon tubules are grown from the precipitation facets and twisted to form a carbon coil. Catalysts with different numbers of active facets and geometric structures form different types of CNCs. [source]

Direct Measurement of Size, Three-Dimensional Shape, and Specific Surface Area of Anatase Nanocrystals

CHEMPHYSCHEM, Issue 6 2007
Armin Feldhoff Dr.
Little is different: The specific surface areas of individual crystal facets on anatase nanocrystals (see picture) are estimated quantitatively by the combination of transmission electron microscope measurements with a Wulff-type construction of the three-dimensional shape. The results demonstrate that the crystal facets that are most abundant for macroscopic crystals are not necessarily those that predominate in nanocrystals. [source]