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 article, C addition (2 wt%) to MoSi2 acted as deoxidant, removing the otherwise ubiquitous siliceous grain boundary phase in hot-pressed samples, and causing formation of SiC and Mo5Si3C1 (a variable-composition Nowotny phase).
Abstract: C addition (2 wt%) to MoSi2 acted as a deoxidant, removing the otherwise ubiquitous siliceous grain boundary phase in hot-pressed samples, and causing formation of SiC and Mo5Si3C1 (a variable-composition Nowotny phase). Both hardness and fracture toughness of the C-containing alloy were higher than those of the C-free (and oxygen-rich) material; more significantly, the fracture toughness of the MoSi2+ 2% C alloy increased from 5.5 MPa·m1/2 at 800°C to ∼11.5 MPa·m1/2 at 1400°C.
149 citations
TL;DR: The use of soluble Mo-S compounds as lubricant additive for reducing friction and wear, increasing load-carrying capacity, promoting fuel economy and as antioxidants is related to their structures and chemical properties.
147 citations
TL;DR: In this paper, the authors summarized methods of preparation, spectroscopic investigations and basic experiments concerning the reactivity of neutral and cationic transition metal carbyne complexes and all known complexes of this type listed based on the experimental results.
146 citations
145 citations
TL;DR: In this article, the need for important metal-non-metal bonds to explain the physical properties of the interstitial phases is pointed out and the conditions for forming half-bonds are discussed, and it is concluded that they may be formed between the nonmetals H, B, C, N and possibly O and the less electropositive A-group metals.
Abstract: Evidence is cited to show that interstitial monocarbides, mononitrides and a few monoxides tend to have the sodium chloride structure irrespective of metal structure and metal radius. The need for important metal–non-metal bonds to explain the physical properties of the interstitial phases is pointed out. Interstitial phases are regarded as electron-deficient structures, where the non-metal forms more bonds than it has bond orbitals. It is suggested that hybrid sp-orbitals combined with p-orbitals are used by the non-metal in bonds to metal. A single p-orbital is used to form two bonds at 180°, but the two bonds or half-bonds contain only one electron pair. Resonance of sp and p bonds leads to octahedral bonding by the non-metal. The concept of half-bonds is used to explain the structure, hardness, brittleness, conductivity and high melting-points of interstitial phases with the sodium chloride-type structure, and a few other interstitial types. The bond distances are consistent with this picture. The conditions for forming half-bonds are discussed, and it is concluded that they may be formed between the non-metals H, B, C, N and possibly O and the less electropositive A-group metals. Only in the case of C, N and O is octahedral bonding and the sodium chloride-type structure to be expected on the basis of the proposal. The proposal also accounts for the limitation of metallic MX compounds with the sodium chloride structure to the third, fourth and fifth group A-metals. The metal–non-metal distances in the interstitial phases agree well with predicted distances for ⅔ or ½ bonds, as given by Pauling's rule.
143 citations