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  • Bleskov, I. D., et al. (författare)
  • Ab initio calculations of elastic properties of Ru1-xNixAl superalloys
  • 2009
  • Ingår i: Applied Physics Letters. - 0003-6951. ; 94:16
  • Tidskriftsartikel (refereegranskat)abstract
    • Ab initio total energy calculations based on the exact muffin-tin orbitals method, combined with the coherent potential approximation, have been used to study the thermodynamical and elastic properties of substitutional refractory Ru1-xNixAl alloys. We have found that the elastic constants C' and C11 exhibit pronounced peculiarities near the concentration of about 40 at. % Ni, which we ascribe to electronic topological transitions. Our suggestion is supported by the Fermi surface calculations in the whole concentration range. Results of our calculations show that one can design Ru-Ni-Al alloys substituting Ru by Ni (up to 40 at. %) with almost invariable elastic constants and reduced density.
  • Isaeva, E. I., et al. (författare)
  • Ab initio phonon calculations for Ll(2) Ni3Al and B2NiAl
  • 2004
  • Ingår i: Solid State Communications. - 0038-1098. ; 129:12, s. 809-814
  • Tidskriftsartikel (refereegranskat)abstract
    • The phonon spectra and phonon density of states of the Ni3Al and NiAl intermetallic compounds are calculated from first principles using the linear response method in conjunction with ultrasoft pseudopotentials. The calculated phonon dispersion curves are in good agreement with available experimental results from inelastic neutron scattering.
  • Loa, I., et al. (författare)
  • Lattice Dynamics and Superconductivity in Cerium at High Pressure
  • 2012
  • Ingår i: Physical Review Letters. - American Physical Society. - 0031-9007. ; 108:4, s. 045502
  • Tidskriftsartikel (refereegranskat)abstract
    • We have measured phonon dispersion relations of the high-pressure phase cerium-oC(4) (alpha phase with the alpha-uranium crystal structure) at 6.5 GPa by using inelastic x-ray scattering. Pronounced phonon anomalies are observed, which are remarkably similar to those of alpha-U. First-principles electronic structure calculations reproduce the anomalies and allow us to identify strong electron-phonon coupling as their origin. At the low-pressure end of its stability range, Ce-oC4 is on the verge of a lattice-dynamical instability and possibly a charge density wave. The superconducting transition temperatures of the fcc, oC4, and mC4 phases of Ce have been calculated, and the superconductivity observed experimentally by Wittig and Probst is attributed to the oC4 phase.
  • Zarechnaya, E. Y., et al. (författare)
  • Theoretical study of linear monoatomic nanowires, dimer and bulk of Cu, Ag, Au, Ni, Pd and Pt
  • 2008
  • Ingår i: Computational materials science. - Institutionen för fysik, kemi och biologi. - 0927-0256. ; 43:3, s. 522-530
  • Tidskriftsartikel (refereegranskat)abstract
    • The binding and electronic properties of monoatomic nanowires, dimers and bulk structures of Cu, Ag, Au and Ni, Pd, Pt have been studied by the projector augmented-wave method (PAW) within the density functional theory (DFT) using the local density approximation (LDA) as well as generalized gradient approximation (GGA) in both Perdew–Wang (PW91) and Perdew–Burke–Ernzerhof (PBE) parameterizations. Our results show that the formation of atomic chains is not equally plausible for all the studied elements. In agreement with experimental observations Pt and Au stand out as most likely elements to form monoatomic wires. Changes in the electronic structure and magnetic properties of metal chains at stretching are analyzed.
  • Belonoshko, Anatoly B., et al. (författare)
  • Stability of the body-centered-tetragonal phase of Fe at high pressure : Ground-state energies, phonon spectra, and molecular dynamics simulations
  • 2006
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 74:21
  • Tidskriftsartikel (refereegranskat)abstract
    • It is well established that at a pressure of several megabars and low temperature Fe is stable in the hexagonal-close-packed (hcp) phase. However, there are indications that on heating a high-pressure hcp phase of Fe transforms to a less dense (open structure) phase. Two phases have been suggested as candidates for these high-temperature stable phases: namely, body-centered-cubic and body-centered-tetragonal (bct) phases. We performed first-principles molecular dynamics and phonon analysis of the bct Fe phase and demonstrated its dynamical instability. This allows us to dismiss the existence of the bct Fe phase under the high-pressure high-temperature conditions of the Earth's inner core.
  • Isaev, E. I., et al. (författare)
  • Dynamical stability of Fe-H in the Earth's mantle and core regions
  • 2007
  • Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424. ; 104:22, s. 9168-9171
  • Tidskriftsartikel (refereegranskat)abstract
    • The core extends from the depth of 2,900 km to the center of the Earth and is composed mainly of an iron-rich alloy with nickel, with 10% of the mass comprised of lighter elements like hydrogen, but the exact composition is uncertain. We present a quantum mechanical first-principles study of the dynamical stability of FeH phases and their phonon densities of states at high pressure. Our free-energy calculations reveal a phonon-driven stabilization of dhcp FeH at low pressures, thus resolving the present contradiction between experimental observations and theoretical predictions. Calculations reveal a complex phase diagram for FeH under pressure with a dhcp -> hcp -> fcc sequence of structural transitions.
  • Ponomareva, A., et al. (författare)
  • Ab initio investigations of surface magnetism in V-Mo
  • 2004
  • Ingår i: Journal of Magnetism and Magnetic Materials. - 0304-8853. ; 272-276, s. 1198-1200
  • Tidskriftsartikel (refereegranskat)abstract
    • Magnetic properties of the (0 0 1) surface of pure vanadium and disordered binary Mo-V alloys have been investigated from the first-principles by means of the LMTO-GF-CPA technique, the fixed spin moment method, and the direct exchange Monte-Carlo statistical mechanics simulations. The binary alloys, as well as pure constituent metals, are nonmagnetic in the bulk. However, we have shown that the (1 0 0) surface of uniformly random and segregated Mo-V alloys is magnetic. The magnetism of the V monolayer on the Mo(0 0 1) surface has also been studied. In particular, the surface relaxation effect has resulted in a reduction of the magnetic moments for V atoms, but the surface magnetism is still present in the system. Including of semi-core states as valence ones does not alter this conclusion. © 2004 Elsevier B.V. All rights reserved.
  • Vekilov, Y. K., et al. (författare)
  • Diamagnetism in quasicrystals
  • 2005
  • Ingår i: Solid State Communications. - 0038-1098. ; 133:7, s. 473-475
  • Tidskriftsartikel (refereegranskat)
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