Occurrence, Extraction, Production and uses of Molybdenum
About: This article is published in Studies in Inorganic Chemistry.The article was published on 1994-01-01. It has received 10 citations till now. The article focuses on the topics: Extraction (chemistry) & Molybdenum.
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TL;DR: In this article, a density functional theory (DFT) analysis of the O 2sp dominated valence band region of MoO 3 was carried out to examine the electronic structure of the oxide systems.
156 citations
TL;DR: In this paper, the structure and electronic properties of the α-MoO3 were studied with periodic LAPW calculations with the results in excellent agreement with the reported experimental pseudo-cubic results.
41 citations
TL;DR: In this paper, the authors performed cluster model studies by means of ab initio DFT method to examine electronic properties of different surface O atoms in several V2O5 and MoO3 systems and correlate them with catalytic behavior.
27 citations
TL;DR: In this paper, the electronic properties of MoO 2 bulk and (0, 1, 1) surface are discussed. But the surface retains the metallic character of the bulk, and it is found that Fermi level is located within the band dominated by d molybdenum orbitals.
Abstract: Electronic properties of MoO 2 bulk and (0 1 1) surface are discussed. It is found that Fermi level is located within the band dominated by d molybdenum orbitals, thereby reflecting the metallic character of the system. Results for (0 1 1)MoO 2 surface indicate that the surface retains the metallic character of the bulk. Depending on the thickness of the slab used to model the surface (1-layer or 2-layers) the electronic structure and properties change. In the 2-layer slab, bands close to the Fermi level originate both from regular six-fold coordinated Mo(6) centers as well as from five-fold coordinated Mo(5) centers occurring due to surface formation. In the 1-layer slab, peaks right below the Fermi level are dominated by the surface centers that are six-fold coordinated Mo(6) but also centers which are effectively four-fold coordinated Mo(4). This has a profound effect on the reactivity as was tested by a probe reaction of H 2 adsorption, which did not interact with the surface described by the 2-layer slab, but underwent dissociation on the 1-layer slab. The Mo–Mo pairs with bonds of approximately single character, characteristic for the bulk structure, are also present on the surface, both on 1-layer and 2-layer slabs. The local properties of (0 1 1)MoO 2 surface are very similar to other transition metal oxides. Metal–oxygen bonds are of a mixed ionic and covalent nature and the nucleophilicity of oxygen increases with the increase of coordination numbers of the corresponding oxygen atoms.
26 citations
TL;DR: In this article, the atomic structure of a reconstructed Mo(1/1/2)-O(2/2/3) surface has been revisited using photoelectron spectroscopy with synchrotron radiation, scanning tunneling microscopy, infrared reflection absorption spectrography and density functional theory.
22 citations
References
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TL;DR: In this paper, a single crystal of TiCx (x=0.84) was exposed to a carbon source at temperatures near 2000°C. The penetration of carbon into the structure, reflected in a gradient in the value of x, was evaluated with the electron microprobe analyzer.
Abstract: Single crystals of TiCx (x=0.84) were exposed to a carbon source at temperatures near 2000°C. The penetration of carbon into the structure, reflected in a gradient in the value of x, was evaluated with the electron microprobe analyzer. The chemical diffusivity D was then determined using the Boltzmann‐Matano method of analysis. The experimental value of D was found to increase with decreasing carbon vacancy concentration, 1−x, and to have the average value of 220 exp (−97 700/RT) cm2/sec. This value of D is in good agreement with one generated from Sarian's 14C tracer measurements on TiC crystals and DePoorter's semitheoretical model for activity. Because of the abundance of vacancies in the carbon fcc sublattice of TiCx, the experimental activation energy represents an energy of motion only. Lower experimental values for the diffusion activation energy have been obtained by other workers with the phase‐boundary advance method. The present work shows that the difference between the activation energy me...
60 citations
TL;DR: In this article, anodic passivating films on iron in phosphate and borate solutions at pH ranging from 1.85 to 11.50 have been analyzed and the optical constant was 3.0-0.5i for the barrier layer and 1.8-Oli for the deposit layer.
Abstract: Ellipsometric measurements and chemical analyses have been carried out of anodic passivating films on iron in phosphate and borate solutions at pH ranging from 1.85 to 11.50. In neutral solutions the passive film consists of an inner oxide barrier layer and an outer hydroxide deposit layer: the optical constant was 3.0—0.5i for the barrier layer and 1.8—O.li for the deposit layer. The barrier layer is potential-dependent and its thickness increases linearly with the potential developing at the steady state a high electric field 5.6 6 V/
55 citations
TL;DR: In this paper, the authors measured the mass spectra, ionization energies, fragmentation energies, ionic and neutral dissociation energies, and heats of formation for the title compounds.
Abstract: Mass spectra, ionization energies, fragmentation energies, ionic and neutral dissociation energies, and heats of formation for the title compounds are measured and compared. Substitution of CS for CO in going from M(CO)/sub 6/ to M(CO)/sub 5/CS results in (a) a slight modification of the mass spectra, if only the M(CO)/sub n/CS/sup +/ and M/sup +/ ions are considered, (b) a lowering of the ionization energies by 0.1 to 0.4 eV, (c) a reduction of approximately 0.1 eV in the average M-CO bond energies in both the molecule and the molecular ion, and (d) a reduction of 3.0 +- 0.3 eV in the heats of formation of the molecules. Within each molecule or molecular ion the M-CS bond is stronger than the M-CO bonds by 1.5 to 2.0 eV. Both the M-CS and the M-CO bonds increase in strength in going from Cr to Mo to W. Comparison of calorimetric and mass spectrometric data for M(CO)/sub 6/ indicates that each neutral CO fragment leaves the ionization site in its first vibrationally excited state. 10 tables.
53 citations
TL;DR: In this article, the authors reported preliminary results for studies of the equilibra in polymolybdate solutions using the LETAC-ROP computer program and showed that the results were similar to those reported in this paper.
Abstract: : Preliminary results are reported for studies of the equilibra in polymolybdate solutions using the LETAC-ROP computer program.
53 citations
51 citations