Electronic structure and spectral properties of Am, Cm and Bk: Charge density self-consistent LDA+HIA calculations in FP-LAPW basis

We provide a straightforward and numerically efficient procedure to perform local density approximation + Hubbard I (LDA+HIA) calculations, including self-consistency over the charge density, within the full potential linearized augmented plane wave (FP-LAPW) method. This implementation is all-electron, includes spin-orbit interaction, and makes no shape approximations for the charge density. The method is applied to calculate selected heavy actinides in the paramagnetic phase. The electronic structure and spectral properties of Am and Cm metals obtained are in agreement with previous dynamical mean-field theory (LDA+DMFT) calculations and with available experimental data. We point out that the charge density self-consistent LDA+HIA calculations predict the $f$ charge on Bk to exceed the atomic integer $f^8$ value by 0.22.Comment: 8 pages, 1 figur

The role of L-carnitine in treatment of a murine model of asthma.

Leukotrienes, one of the mediators of inflammation in asthma, have a strong bronchoconstrictive effect. L-carnitine has been reported to influence respiratory functions. It has also been reported that L-carnitine inhibits leukotriene synthesis. To evaluate the effects of L-carnitine on oxygen saturation, urine leukotriene E4 levels and lung histopathology in a murine model of asthma, high IgE responder BALB/c mice (n = 24) were systemically sensitized to ovalbumin and chronically challenged with low particle mass concentrations of aerosolized ovalbumin, and then they were divided into 3 groups (study groups A, B, and C) each including eight mice. After methacholine-induced bronchoconstriction, the mice in groups A and B were given intraperitoneal L-carnitine (250 and 125 mg/kg, respectively), while the mice in group C were given placebo. Oxygen saturation of the mice was measured by pulse oxymeter before and after methacholine and after L-carnitine/ placebo application. In addition, urine leukotriene E4 levels were measured before asthma development, and 24-h after L-carnitine injection in asthmatic mice. Inflammation in the lung tissues of the sacrificed animals was scored histopathologically to determine the effect of L-carnitine on tissue level. A control group of non-sensitized mice (n = 8) treated with placebo only was used for comparison of urine leukotriene E4 levels and of histopathological parameters. Oxygen saturation of the mice in the study groups tended to decrease after methacholine and to improve after L-carnitine injection, although these changes were not significant at all time points. Urine leukotriene E4 levels of all 3 study groups increased significantly after asthma development. The rate of increment was smallest in the group given the highest L-carnitine dose (group A). Inflammation at the tissue level was also mildest in group A, and severest in the group that was not given carnitine (group C). All of the study groups and the control group differed significantly with respect to inflammation scores. In conclusion, L-carnitine improved oxygen saturation, and decreased urine leukotriene E4 levels and inflammation in lung tissues in the present murine model of asthma.</p

Adsorption and dissociation of molecular oxygen on the (0001) surface of double hexagonal close packed americium

In our continuing attempts to understand theoretically various surface properties such as corrosion and potential catalytic activity of actinide surfaces in the presence of environmental gases, we report here the first ab initio study of molecular adsorption on the double hexagonal packed (dhcp) americium (0001) surface. Dissociative adsorption is found to be energetically more favorable compared to molecular adsorption. The most stable configuration corresponds to a horizontal approach molecular dissociation with the oxygen atoms occupying neighboring h3 sites, with chemisorption energies at the NSOC and SOC theoretical levels being 9.395 eV and 9.886 eV, respectively. The corresponding distances of the oxygen molecule from the surface and oxygen-oxygen distance were found to be 0.953 Ang. and 3.731 Ang., respectively. Overall our calculations indicate that chemisorption energies in cases with SOC are slightly more stable than the cases with NSOC in the 0.089-0.493 eV range. The work functions and net magnetic moments respectively increased and decreased in all cases compared with the corresponding quantities of the bare dhcp Am (0001) surface. The adsorbate-substrate interactions have been analyzed in detail using the partial charges inside the muffin-tin spheres, difference charge density distributions, and the local density of states. The effects, if any, of chemisorption on the Am 5f electron localization-delocalization characteristics in the vicinity of the Fermi level are also discussed.Comment: 6 tables, 10 figure

Probing the 5f Electrons in Am-I by Hybrid Density Functional Theory

The ground states of the actinides and their compounds continue to be matters of considerable controversies. Experimentally, Americium-I (Am-I) is a non-magnetic dhcp metal whereas theoretically an anti-ferromagnetic ground state is predicted. We show that hybrid density functional theory, which admixes a fraction of exact Hartree-Fock (HF) exchange with approximate DFT exchange, can correctly reproduce the ground state properties of Am. In particular, for a 0.40 fraction of HF exchange we obtain a non-magnetic ground state with equilibrium atomic volume, bulk modulus, 5f electron population, and the density of electronic states all in good agreement with experimental data. We argue that the exact HF exchange corrects the overestimation of the approximate DFT exchange interaction.Comment: 1 table, 4 figures. Chemical Physics Letters, in press (2009

A Density Functional Study of Atomic Hydrogen and Oxygen Chemisorption on the Relaxed (0001) Surface of Double Hexagonal Close Packed Americium

Ab initio total energy calculations within the framework of density functional theory have been performed for atomic hydrogen and oxygen chemisorption on the (0001) surface of double hexagonal packed americium using a full-potential all-electron linearized augmented plane wave plus local orbitals method. Chemisorption energies were optimized with respect to the distance of the adatom from the relaxed surface for three adsorption sites, namely top, bridge, and hollow hcp sites, the adlayer structure corresponding to coverage of a 0.25 monolayer in all cases. Chemisorption energies were computed at the scalar-relativistic level (no spin-orbit coupling NSOC) and at the fully relativistic level (with spin-orbit coupling SOC). The two-fold bridge adsorption site was found to be the most stable site for O at both the NSOC and SOC theoretical levels with chemisorption energies of 8.204 eV and 8.368 eV respectively, while the three-fold hollow hcp adsorption site was found to be the most stable site for H with chemisorption energies of 3.136 eV at the NSOC level and 3.217 eV at the SOC level. The respective distances of the H and O adatoms from the surface were found to be 1.196 Ang. and 1.164 Ang. Overall our calculations indicate that chemisorption energies in cases with SOC are slightly more stable than the cases with NSOC in the 0.049-0.238 eV range. The work functions and net magnetic moments respectively increased and decreased in all cases compared with the corresponding quantities of bare dhcp Am (0001) surface. The partial charges inside the muffin-tins, difference charge density distributions, and the local density of states have been used to analyze the Am-adatom bond interactions in detail. The implications of chemisorption on Am 5f electron localization-delocalization are also discussed.Comment: 9 Tables, 5 figure

On the Convergence of the Electronic Structure Properties of the FCC Americium (001) Surface

Electronic and magnetic properties of the fcc Americium (001) surface have been investigated via full-potential all-electron density-functional electronic structure calculations at both scalar and fully relativistic levels. Effects of various theoretical approximations on the fcc Am (001) surface properties have been thoroughly examined. The ground state of fcc Am (001) surface is found to be anti-ferromagnetic with spin-orbit coupling included (AFM-SO). At the ground state, the magnetic moment of fcc Am (001) surface is predicted to be zero. Our current study predicts the semi-infinite surface energy and the work function for fcc Am (001) surface at the ground state to be approximately 0.82 J/m2 and 2.93 eV respectively. In addition, the quantum size effects of surface energy and work function on the fcc Am (001) surface have been examined up to 7 layers at various theoretical levels. Results indicate that a three layer film surface model may be sufficient for future atomic and molecular adsorption studies on the fcc Am (001) surface, if the primary quantity of interest is the chemisorption energy.Comment: 34 pages, 9 figure

Electronic structure and magnetic state of transuranium metals under pressure

Electronic structure of bcc Np, fcc Pu, Am, and Cm pure metals under pressure has been investigated employing the LDA+U method with spin-orbit coupling (LDA+U+SO). Magnetic state of the actinide ions was analyzed in both LS and jj coupling schemes to reveal the applicability of corresponding coupling bases. It was demonstrated that whereas Pu and Am are well described within the jj coupling scheme, Np and Cm can be described appropriately neither in {m-sigma}, nor in {jmj} basis, due to intermediate coupling scheme realizing in these metals that requires some finer treatment. The LDA+U+SO results for the considered transuranium metals reveal bands broadening and gradual 5f electron delocalization under pressure.Comment: 5 pages, 5 figure

Data Structures with Java

For a freshman/sophomore-level course in Data Structures in Computer Science. This text teaches the use of direct source code implementations and the use of the Java libraries; it helps students prepare for later work on larger Java software solutions by adhering to software engineering principles and techniques such as the UML and the Java Collections Framework (JCF). Using the spiral approach to cover such topics as linked structures, recursion, and algorithm analysis, this text also provides revealing illustrations, summaries, review questions, and specialized reference sections.https://scholarship.richmond.edu/bookshelf/1129/thumbnail.jp