ExxonMobil

About: ExxonMobil is a company organization based out in Irving, Texas, United States. It is known for research contribution in the topics: Catalysis & Polymerization. The organization has 16969 authors who have published 23758 publications receiving 535713 citations. The organization is also known as: Exxon Mobil Corporation & Exxon Mobil Corp..

Systematic variation of magnetic-field penetration depth in high- T c superconductors studied by muon-spin relaxation

Abstract: The muon relaxation rate (sigma) was measured in the high critical temperature superconductors YBa2Cu3O(x) for x = 6.66, 6.95, 7.0, and La1.85 SrO.15 CuO4 in transverse external magnetic fields 1 is approximately 4 kG. A simple relation is found which connects the transition temperature T(c), the magnetic field penetration depth lambda(L), the carrier concentration n(s) and the effective mass m* as T(c) varies as sigma which varies as 1/lambda(L) squared which varies as n(s)/m*. The linear dependence T(c) varies as n(s)/m* suggests a high energy scale for the coupling between superconducting carriers.

Localization in One-Dimensional Lattices in the Presence of Incommensurate Potentials

Abstract: The density of states and the localized or extended nature of the eigenstates is investigated in one-dimensional crystals with a modulation potential incommensurate with that of the underlying lattice. Studies of the transmission coefficient $T$ and of the spatial dependence of the eigenstates show that even in one dimension it is possible to have a mobility edge. The implications of these results on experimentally measured quantities are also discussed.

First-principles linear combination of atomic orbitals method for the cohesive and structural properties of solids: Application to diamond

Abstract: We present a new method for the ab initio calculation of the cohesive and structural properties of solids. The method is based upon a linear combination of atomiclike orbitals (LCAO). Thus it possesses the physical appeal of traditional LCAO approaches. The method is a "first principles" one in the sense that no adjustable parameters enter the calculation. The required overlap integrals are calculated directly in real space. The one-electron potentials are derived from atomic properties and correspond to "ab initio" pseudopotentials. Another aspect of the method is that it does not involve a fully-self-consistent-field solution of the Schr\"odinger equation. Rather, the total energy of the system is obtained by using a noniterative approach based explicitly on the variational principle in the density-functional formalism. The method is applied to an archtypical covalent system: the diamond crystal. Several ground-state properties---including the cohesive energy, lattice constant, the bulk modulus, and the derivative of the bulk modulus with pressure---are computed. The computed lattice constant and bulk modulus are within 1-2% of the experimental values and the computed cohesive energy is within 10% of the experimental value. Also, we present a frozen-phonon calculation for the optical phonons at the Brillouin-zone center and obtain agreement to within 1% of the experimental value.

Distillate fuel production from fischer-tropsch wax

Abstract: Distillate fuels with excellent cold flow properties are produced from waxy Fischer-Tropsch products by separating the product into a heavier and a lighter fraction, isomerizing the heavier fraction, hydrotreating and isomerizing the lighter fraction, and recovering products in jet and diesel fuel ranges.

Preparation of the First Molecular Carbon Monoxide Complex of Uranium, (Me3SiC5H4)3UCO

Abstract: Migratory insertion of an anionic group onto coordinate carbon monoxide or an isocyanide is an important mechanistic postulate in organoactinide chemistry. In contrast to transition metals, where carbon monoxide complexes abound, only three examples of carbon monoxide coordination to uranium have been observed in matrix isolation studies at cyrogenic temperatures. These studies showed that U(CO)/sub 6/ can exist below ca. 20 K and that nu/sub CO/ of 1961 cm/sup -1/ is similar to that found for W(CO)/sub 6/, nu/sub CO/ is 1987 cm/sup -1/ under similar conditions. The nu/sub CO/ is lowered substantially from gaseous CO (nu = 2145 cm/sup -1/) which implies that uranium metal is a ..pi..-donor, though the bonds are either kinetically labile, thermodynamically weak, or both. In UF/sub 4/(CO) the nu/sub CO/ of 2182 cm/sup -1/ at 20 K/sup 2c/ shows that the tetravalent compound does not engage in ..pi..-back-bonding to CO. In another study, UO/sub 2/ has been shown to absorb CO at temperatures below 20 K; the CO stretching frequency was not measured. In this paper, evidence is given for (Me/sub 3/SiC/sub 5/H/sub 4/)/sub 3/UCO, the first molecular actinide complex of carbon monoxide in solution and solid phase. 8 references.