D. V. Suetin

Structural, electronic and magnetic properties of η carbides (Fe3W3C, Fe6W6C, Co3W3C and Co6W6C) from first principles calculations

First-principles FLAPW-GGA calculations have been performed with the purpose to determine the peculiarities of the structural, electronic, magnetic properties and stability for a family of related η carbides M3W3C and M6W6C (where M=Fe and Co). The geometries of all phases were optimized and their structural parameters, theoretical density, cohesive and formation energies, total and partial densities of states, atomic magnetic moments have been obtained and analyzed in comparison with available theoretical and experimental data.

Electronic properties of hexagonal tungsten monocarbide (h-WC) with 3d impurities from first-principles calculations

Abstract First-principles FLAPW-GGA calculations have been performed to predict the structural, electronic, cohesive and magnetic properties for hexagonal tungsten monocarbide (h-WC) doped with all 3d metals. The optimized lattice parameters, density of states, cohesive and formation energies have been obtained and analyzed for ternary solid solutions with nominal compositions W0.875M0.125C (where M=Sc, Ti…Ni, Cu). In addition, the magnetic properties of these solid solutions have been examined, and magnetization has been established for W0.875Co0.125C.

Electronic, magnetic properties and correlation effects in the layered quaternary iron oxyselenide Na2Fe2Se2O from first principles

Abstract By means of the first-principle calculations, we have investigated electronic, magnetic properties and correlation effects for the newly discovered layered oxyselenide Na 2 Fe 2 Se 2 O. Our results reveal that the electron correlations in the Fe 3 d bands promote a transition of Na 2 Fe 2 Se 2 O from magnetic metallic or half-metallic states to the antiferromagnetic Mott-insulating state. The bonding picture in Na 2 Fe 2 Se 2 O is examined and described as an anisotropic mixture of ionic and covalent contributions.

The influence of oxygen deficiency on structural and electronic properties of layered superconductor (Fe2As2)(Sr4V2O6−x)

By means of the first-principles FLAPW-GGA approach, we studied the influence of oxygen deficiency on the structural and electronic properties of the superconducting phase (Fe2As2)(Sr4V2O6−x). We find that the formation of vacancies in 2c sites of oxygen sublattice [when the initial tetragonal structure of the stoichiometric crystal (Fe2As2)(Sr4V2O6) is kept] is energetically more preferable than in 4f sites, when orthorhombic distortions arise. The influence of oxygen vacancies on the structure of (Fe2As2) blocks is very insignificant; thus, using the known structural indicators, it is impossible to explain the observed drop of transition temperature TC for oxygen-deficient systems by structural factors. On the other hand, the results of the band structure calculations allow us to assert that the vacancy-induced drop of TC may be caused by the electronic factor, i.e., by the established decrease in Ntot(EF) for the oxygen-deficient system.

Electronic Structure, Mechanical and Dynamical Stability of Hexagonal Subcarbides M 2 C (M = Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt): Ab Initio Calculations

Ab initio calculations were used to study the properties of a series of hexagonal (Fe2N-like) subcarbides M2C, where M = Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt, and to calculate their equilibrium structural parameters, electronic properties, phase stability, elastic constants, compression modulus, shear modulus, Young’s modulus, compressibility, Pugh’s indicator, Poisson ratio, elastic anisotropy indices, and also hardness, Debye temperature, sound velocity, and low-temperature heat capacity. It is found based on these results that all the subcarbides are mechanically stable; however, their formation energies Eform are positive with respect to a mixture of d-metal and graphite. In addition, the calculation of the phonon spectra of these subcarbides shows the existence of negative modes, which indicates their dynamical instability. Thus, a successful synthesis of these subcarbides at normal conditions is highly improbable.

Electronic and mechanical properties, phase stability, and formation energies of point defects of niobium boronitride Nb 2 BN

The electronic structure, Fermi surface, Sommerfeld and Pauli paramagnetic susceptibility coefficients, cohesive energies, phase and point defect formation energies, elastic constants, bulk, shear, and Young moduli, Poisson ratios, and Vickers microhardness of niobium boronitride Nb2BN are determined by the ab initio FLAPW-GGA full-potential method. The obtained values are discussed in comparison with similar data for Mo2BC and other related binary carbides, nitrides, and borides of transition metals, and with available experimental data.

Effect of 4d metal impurities on the structure, electronic properties, and stability of hexagonal WC from data of FLAPW-GGA calculations

This paper reports on the results of systematic ab initio full-potential linearized augmented plane wave (FP-LAPW) calculations of the band structure and a number of properties of hexagonal tungsten carbide h-WC doped by all 4d metals (M = Y, Zr, ..., Ag). The lattice parameters, distributions of the density of states, energies of formation and cohesion, low-temperature heat capacity coefficients, and Pauli paramagnetic susceptibilities of the WC: M systems have been determined for the first time and discussed in comparison with those for h-WC doped by 3d atoms. It has been found that the change in these properties of the WC: M systems as a function of the type of M atom has a nonmonotonic character.