Search results for "Surface structure"
showing 10 items of 29 documents
Effects of post-growth annealing on structural and compositional properties of the Co2Cr0.6Fe0.4Al surface and its relevance for the surface electron…
2009
In this study we investigate the influence of post-growth annealing on different Co2Cr0.6Fe0.4Al samples. We find strong changes in the geometric surface structure as well as in the element specific concentrations during the annealing process. These irreversible changes go in hand with characteristic changes in the electron spin polarization (ESP) at the surface: as observed in Cinchetti et al (2007 J. Phys. D: Appl. Phys. 40 1544), the iron buffered sample shows the largest spin polarization at the Fermi level. The latter remains positive as a consequence of the reduced density of states for the minority carriers due to the predicted minority gap, which can be clearly seen for all samples …
Calculations of the atomic structure of the KNbO3 (110) surface
2000
Abstract The O-terminated KNbO 3 (110) surface is modeled using a semi-empirical shell model and two different short-range interatomic potentials. We find this surface to be unstable with respect to a strong reconstruction and K-termination. This conclusion is confirmed by preliminary calculations using the ab initio linear combination of atomic orbitals (LCAO) formalism.
Elastohydrodynamic Collision of Two Spheres Allowing Slip on Their Surfaces.
2000
Our goal is to study theoretically the effect of deformation on the collision of two solid spheres allowing slip on their surfaces. The deformed shape of the solid surface is determined via an asymptotic technique assuming that deformation is small compared with the separation between the surfaces. It has previously been shown that the slippage makes collision possible even without any surface attractive force. Here we demonstrate that even a small amount of deformation can preclude spheres from coagulation. Copyright 2000 Academic Press.
New advances in the 3D characterization of mineral coating layers on paper
2008
Summary The surface characteristics of a large set of commercial lightweight coated paper grades are explored. The quantification of the 3D structure is revealed by atomic force microscopy, laser profilometry and X-ray microtomography. This comprehensive study demonstrates the suitability of different and modern methods for assessing critical coating layer properties, thus identifying the right tools for specific structural analyses. Based on the assessment of the top and bottom surfaces of 25 commercial lightweight coated samples, three main conclusions can be drawn: (1) the facet orientation polar angle is a function of roughness, (2) skewness did not describe the surface details affectin…
Removal of Escherichia coli from Saturated Sand Columns Supplemented with Hydrochar Produced from Maize
2014
Despite numerous studies on hydrochar use, its application in water treatment for pathogen removal remains unexplored. In this study, we evaluated the efficiency of hydrochar produced from crop residue of maize for water treatment by determining Escherchia coli breakthrough from sand columns supplemented with hydrochar. To enhance the adsorptive capacity, raw hydrochar was activated by 1 mol L⁻¹ KOH at room temperature. The experiments conducted in a 10-cm sand bed with 1.5% (w/w) activated and raw hydrochar supplements, not activated by KOH, showed 93 and 72% of E. coli removal efficiencies, respectively. Activation of KOH not only enhanced the E. coli removal but also increased the streng…
Numerical Modelling of the Urban Climate
1988
Three-dimensional numerical models of the urban climate have been developed in order to simulate climatic changes and air pollution in urban regions due to anthropogenic activities. Two versions are presented. Model A covers mesoscale γ and uses the roughness length to characterize surface structure. The microscale version B approximates the actual urban build-up by rectangular blocks. Model A results agree reasonably well with observations. For complex building structures, the microscale model must be applied. Model B results on neutral flow and pollutant transport within a particular building configuration are discussed.
Mo(CO)6 dissociation on Cu(111) stimulated by a Scanning Tunneling Microscope
2013
Abstract The surface of Cu(111) was exposed to molybdenum hexacarbonyl Mo(CO)6 with monolayer coverage at temperature 160 K and studied by a Scanning Tunneling Microscope. The monolayer structure has a hexagonal arrangement and forms a (√7 × √7) R19 superlattice on the copper (111) plane. Upon repeated scanning the monolayer is transformed into a (1 × 2) superstructure with 3-fold oriented domains. The domains of (1 × 2) superstructure can change orientation under scanning according to 3-fold surface symmetry. From analysis of the domain mobility, it follows that CO groups of carbonyl fragments are organized in the (1 × 2) superstructure conditioning the domain reorientation. The observed s…
Atomistic simulation of the [001]surface structure in BaTiO3
1997
Abstract We simulate the effect of the surface relaxation on the polarization of the layers of paraelectric phase in the vicinity of the [001] surface in BaTiO 3 in the framework of the shell-model potentials. We observe large polarization of ions in the first two layers of the surface. Our simulations confirm the possibility of existence of Ti- and Ba-containing top layers in [001] BaTiO 3 surfaces.
Focus on the Essential: Extracting the Decisive Energy Barrier of a Complex Process
2019
Molecular processes at surfaces can be composed of a rather complex sequence of steps. The kinetics of even seemingly simple steps are demonstrated to depend on a multitude of factors, which prohibits applying a simple Arrhenius law. This complexity can make it challenging to experimentally determine the kinetic parameters of a single step. However, a molecular-level understanding of molecular processes such as structural transitions requires elucidating the atomistic details of the individual steps. Here, a strategy is presented to extract the energy barrier of a decisive step in a very complex structural transition by systematically addressing all factors that impact the transition kineti…
Layer-by-Layer Graphene Growth on β-SiC/Si(001)
2019
ACS nano 13(1), 526 - 535 (2019). doi:10.1021/acsnano.8b07237