Search results for "Faces"
showing 10 items of 3167 documents
Fluorination of Cu(001) Surface by C60F48 Molecule Adsorption
2019
Copper surface functionalization by defluorination of C60F48 molecules with submonolayer and monolayer coverages on the Cu(001) crystal is studied by X-ray photoelectron spectroscopy. At room tempe...
Discrimination of nerve gases mimics and other organophosphorous derivatives in gas phase using a colorimetric probe array.
2012
A colorimetric array for the chromogenic discrimination of organophosphorous derivatives in gas phase has been developed. The array allows us to classify the nerve agent simulants DFP, DCP and DCNP.
The kinetic MC modelling of reversible pattern formation in initial stages of thin metallic film growth on crystalline substrates
2003
Abstract The results of kinetic MC simulations of the reversible pattern formation during the adsorption of mobile metal atoms on crystalline substrates are discussed. Pattern formation, simulated for submonolayer metal coverage, is characterized in terms of the joint correlation functions for a spatial distribution of adsorbed atoms. A wide range of situations, from the almost irreversible to strongly reversible regimes, is simulated. We demonstrate that the patterns obtained are defined by a key dimensionless parameter: the ratio of the mutual attraction energy between atoms to the substrate temperature. Our ab initio calculations for the nearest Ag–Ag adsorbate atom interaction on an MgO…
Probing the Multiple Structures of Vaterite through Combined Computational and Experimental Raman Spectroscopy.
2014
First-principles Raman spectra have been computed for several new vaterite structural models that have been recently proposed, and compared with spectra recorded on a set of biogenic, geological and synthetic samples. This set includes new measurements collected on Herdamania momus spicules (Great Barrier Reef, Queensland, Australia), which are known to have purity and crystallinity that are higher than for other biogenic samples. Overall, due to the close structural connection between the various models, the computed Raman spectra are found to be broadly similar. However, the spectra obtained for the two most stable models (monoclinic C2 and trigonal P3221, corresponding to two different p…
The adhesion properties of the Ag/α-Al2O3() interface: an ab initio study
2002
Ab initio computer simulations of the atomic and electronic structure of the Ag/a-Al2O3(0 0 0 1) (corundum) interface have been performed for a periodic two-dimensional slab model using the Hartree–Fock method and a posteriori electron correlation corrections.We have considered both Al- and O-terminated corundum substrate surfaces.The dependence of the adhesion energy on the interfacial distance has been analyzed for the two most favorable Ag adsorption positions over corundum and for two different metal coverages (a 1/3 monolayer (ML) of the Ag(1 1 1) crystallographic plane and a full Ag(1 1 1) monolayer).The two different terminations (Al- and O-) give rise to qualitatively different resu…
Metal film growth on regular and defective MgO(001) surface: A comparative ab initio simulation and thermodynamic study
2006
Abstract In order to understand the difference in metallic film growth modes on perfect and defective oxide substrates, we have combined ab initio B3LYP periodic calculations on the slab models of the corresponding Me/MgO(0 0 1) interfaces (Me = Ag, Cu) with thermodynamic theory of solid solutions. For a defectless magnesia surface, we confirm the experimentally observed submonolayer growth of 3D metallic islands (Ag possesses a higher trend than Cu). Formation of Fs centers (neutral O vacancies) on the substrate markedly enhances metal atom adsorption as compared to physisorption over regular sites on a defect-free substrate. For the first time, we predict that the presence of these surfac…
BacSr1−cTiO3 perovskite solid solutions: Thermodynamics from ab initio electronic structure calculations
2005
We suggest theoretical prediction for Ba"cSr"1"-"cTiO"3 perovskite solid solutions (BST) combining ab initio DFT/B3PW calculations and alloy thermodynamics. This approach is based on calculations of a series of ordered super-structures in Ba-Sr simple cubic sublattice immersed in the rest TiO"3 matrix. Although these structures are unstable with respect to the decomposition, the results of total energy calculations allow us to extract the necessary energy parameters and to calculate the phase diagram for the solid solutions (alloys). A novel approach applied to the BST system enables to predict that at T>400 K Ba and Sr atom distribution is random. But below this temperature at small c Ba a…
Quantitative phase analysis and thickness measurement of surface-oxide layers in metal and alloy powders by the chemical-granular method
1998
The principles of the chemical-granular analysis of metal and alloy powders are reviewed and the results are compared with those provided by the spectroscopic analytical techniques XPS, AES and SIMS, including ion etching in their depth-profiling mode, when they are applied to the same materials. Several examples are analysed and it is shown that the chemical-granular method alone can provide the very same information as depth profiling. However, it is averaged over a macroscopic powder sample in contrast to one or a few single particles. Nevertheless, it is the combination of the chemical-granular and depth-profiling analyses that really provides an unparalleled description in quantitative…
The structure of pumice: An XPS and27Al MAS NMR study
1992
In order to investigate the surface structure of pumice, an amorphous aluminosilicate, samples of pumice and of standards of silica and alumina have been studied by x-ray photoelectron spectroscopy (XPS). The effect of a mild acid leaching was also considered. The analysis of the Si 2p, Al 2p and O 1s photoelectron peaks and the Si KLL and O KLL Auger peaks indicated that pumice is formed by tetrahedral silica with some units being replaced by aluminate, AlO2−. The acid treatment decreases the alkali and the aluminate ions. X-ray photoelectron spectra of the valence band of pumices and of standards of Al2O3 and SiO2 agree with the core-level results. To support the conclusions from the XPS …
Molecular Dynamics Simulations of SFG Librational Modes Spectra of Water at the Water–Air Interface
2016
At the water–air interface, the hydrogen-bond network of water molecules is interrupted, and accordingly, the structure and dynamics of the interfacial water molecules are altered considerably compared with the bulk. Such interfacial water molecules have been studied by surface-specific vibrational sum-frequency generation (SFG) spectroscopy probing high-frequency O–H stretch and H–O–H bending modes. In contrast, the low-frequency librational mode has been much less studied with SFG. Because this mode is sensitive to the hydrogen-bond connectivity, understanding the librational mode of the interfacial water is crucial for unveiling a microscopic view of the interfacial water. Here, we compu…