Fe-family of superconductors: Influence of Ni dopant on the superconductivity in BaFe2As2 crystal and the relaxation volume

ABSTRACTThe doped iron arsenides present outstanding properties, one of them is an unconventional superconductivity, an unusual coexistence of superconductivity and magnetism. We calculated the electronic structure of the pure and Ni-doped BaF e2As2 by the embedded cluster method at the electron correlation level; the latter is calculated through the second- order Møller Plesset perturbation theory. For the doped clusters, we calculated the relaxation of the first and second neighbors of the impurity by optimizing their positions in the cluster. The total electronic density is analyzed through natural bond orbitals and the population of each atomic orbital (basis function) is determined; the robustness of this determination is tested comparing results obtained for the unrelaxed and relaxed cluster. The orbital population analysis uncovers some properties of magnetism and superconductivity in BaFe2As2. From our results, linear elasticity allows us to estimate the relaxation volume of Ni impurity.

Reaction of aniline with ammonium persulphate and concentrated hydrochloric acid: Experimental and DFT studies

In this paper, the reaction of aniline with ammonium persulphate and concentrated HCl was studied. As a result of our experimental studies, 2,4,6-trichlorophenylamine was identified as the main product. This shows that a high concentration of HCl does not favour oxidative polymerisation of phenylamine, even though the ammonium persulphate/HCl system is widely used in polyaniline synthesis. On the basis of the experimental data and density functional theory for reaction path modelling, we proposed a mechanism for oxidative chlorination of aniline. We assumed that this reaction proceeded in three cyclically repeated steps; protonation of aniline, formation of singlet ground state phenylnitrenium cation, and nucleophilic substitution. In order to confirm this mechanism, kinetic, thermochemical, and natural bond orbital population analyses were performed.

Theoretical Investigation on Structures and Stabilities of CuXenZ (n = 1 - 3, Z = - 1, 0, +1) Clusters

The structures and stabilities of CuXe n Z (n = 1–3, Z = –1, 0, +1) cluster series at the CCSD(T) theoretical level have been investigated. Herein, it is shown that the cations are more stable and have more compact geometries than the anions and neutrals. The role of the interaction is explained using the natural bond orbital, population, and electron density analysis.

Comparative analysis of the trypanocidal activity and chemical properties of E-lychnophoric acid and its derivatives using theoretical calculations

E-Lychnophoric acid 1, its derivative ester 2 and alcohol 3 killed 100% of trypomastigote blood forms of Trypanosoma cruzi at the concentrations of 13.86, 5.68, and 6.48 µg/mL, respectively. Conformational distribution calculations (AM1) of 1, 2 and 3 gave minimum energies for the conformers a, b, c, and d, which differ from each other only in the cyclononene ring geometry. Calculations (DFT/BLYP/6-31G*) of geometry optimization and chemical properties were performed for conformers of 1, 2, and 3. The theoretical results were numerically compared to the trypanocidal activity. Calculated values of atomic charge, orbital population, and vibrational frequencies showed that the C-4-C-5 pi-endocyclic bond does not affect the trypanocidal activity of the studied compounds. Nevertheless, the structure of the group at C-4 strongly influences the activity. However, the theoretical results indicated that the intra-ring (C-1 and C-9) and pi-exocycle (C-8 and C-14) carbons of caryophyllene-type structures promote the trypanocidal activity of these compounds.

THE EFFECT OF H ON THE ELECTRONIC STRUCTURE OF AN Fe(110)–Pd(100) INTERFACE

The ion-driven mechanism in hydrogen permeation is substantially modified when iron is coated with palladium. A detailed knowledge of the electronic structure at the metal–metal interfaces is a prerequisite for understanding the process of H permeation. We have selected two low-Miller-index surfaces as a simple model for the interface. The system under consideration has 148 metallic atoms forming an Fe–Pd cluster distributed in six metallic layers. We have investigated the interaction of atomic hydrogen with the Fe (110)– Pd (100) interface using the semiempirical atom superposition and electron delocalization (ASED-MO) method. The changes in the electronic structures, density of states (DOS) and crystal overlap orbital population (COOP) in two different Fe–Pd interfaces were compared with the bulk ground states of both metals. The interfacial Fe–Pd distance results in about 1.74 Å, whereas for the Fe–Pd first neighbors distance it is about 1.85 Å. An important conclusion is that the metal–metal bonds at the interface are stronger than those bonds in the pure metal bulk. A favorable metal adhesion is observed, as revealed by the energetic stabilization of the composite metal system. H is stabilized near the FePd interface and stopped at the first Pd layer. A H–metal bond is developed with both Fe and Pd atoms while Fe–Pd bonding at the interface remains unaltered.

Nucleophilic addition reaction in coordinated non-linear pseudohalides: experimental charge density analysis in trans-bis(cyanamidonitrato-N:O)bis-(imidazole-N 3)copper(II) complex

The experimental crystal charge density of the complex [Cu(iz)2(can)2] (I) (where iz = imidazole, can = cyanamidonitrate anion), [Cu(C3H4N2)2(CN3O2)2], crystallizing in centrosymmetric space group P21/c, has been determined at 120.0 (2) K, using Hansen and Coppens' aspherical atom multipole model. The central Cu atom is pseudo-octahedrally coordinated by four N atoms in an equatorial plane [two from iz molecules, 1.9660 (4) Å, two from can anions, 2.0273 (5) Å] and by two O atoms (from two adjacent molecules) in axial positions [2.5566 (5) Å]. The d-orbital population analysis shows that the oxidation state for the copper is +2 with the d 9 configuration and that there is a hole in the d_{x^2 - y^2} orbital, located in the plane of the four nitrogen-ligating atoms. Electron lone pairs of these four N atoms are pointing into these regions of depleted electron density. In accordance with the medium-length Cu—O axial bonds, the d z2 orbital is almost fully occupied [1.79 (3) electrons]. The non-bonding d xy orbital is fully occupied [2.05 (3) electrons]. Analysis of the atomic charges does indicate a deficit of +0.35 (4) e− on the nitrile carbon, which provides evidence of β-carbon activation for a possible nucleophilic addition reaction. This reaction has been indirectly confirmed experimentally.