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Träfflista för sökning "LAR1:uu ;pers:(Ahuja Rajeev);srt2:(2000-2004)"

Sökning: LAR1:uu > Ahuja Rajeev > (2000-2004)

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2.
  • Ahuja, Rajeev, et al. (författare)
  • Optical properties of 4H-SiC
  • 2002
  • Ingår i: Journal of Applied Physics. - 0021-8979. ; 91:3, s. 2099-2103
  • Tidskriftsartikel (refereegranskat)abstract
    • The optical band gap energy and the dielectric functions of n-type 4H-SiC have been investigated experimentally by transmission spectroscopy and spectroscopic ellipsometry and theoretically by an ab initio full-potential linear muffin-tin-orbital method. We present the real and imaginary parts of the dielectric functions, resolved into the transverse and longitudinal photon moment a, and we show that the anisotropy is small in 4H-SiC. The measurements and the calculations fall closely together in a wide range of energies. © 2002 American Institute of Physics.
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  • Belonoshko, A. B., et al. (författare)
  • High-pressure crystal structure studies of Fe, Ru and Os
  • 2004
  • Ingår i: Journal of Physics and Chemistry of Solids. - 0022-3697. ; 65:09-aug, s. 1565-1571
  • Tidskriftsartikel (refereegranskat)abstract
    • In order to reveal structural trends with increasing pressure in d transition metals, we performed full potential linear muffin-tin orbital calculations for Fe, Ru, and Os in the hexagonal close packed structure. The calculations cover a wide volume range and demonstrate that all these hexagonal close-packed metals have non-ideal c/a at low pressures which, however, increases with pressure and asymptotically approaches the ideal value at very high compressions. These results are in accordance with most recent experiment for Ru and Os. The experimental data for iron is not conclusive, but it is believed that the c/a ratio decreases weakly with increasing pressure at moderate compression. Since, the experimental and calculated equations of state for iron are in increasingly good agreement with increasing pressure, it is possible that either the negative c/a trend is valid only for a restricted pressure range, or related to the experimental difficulties (e.g. non-hydrostaticity).
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5.
  • Belonoshko, Anatoly B., et al. (författare)
  • Molecular dynamics study of melting and fcc-bcc transitions in Xe
  • 2001
  • Ingår i: Physical Review Letters. - 0031-9007. ; 8716:16, s. art. no.-165505
  • Tidskriftsartikel (refereegranskat)abstract
    • We have investigated the phase diagram of Xe over a wide pressure-temperature range by molecular dynamics. The calculated melting curve is in good agreement with earlier experimental data. At a pressure of around 25 GPa and a temperature of about 2700 K we find a triple fcc-bcc liquid point. The calculated fcc-bcc boundary is in nice agreement with the experimental points, which, however, were interpreted as melting. This finding suggests that the transition from close-packed to bcc structure might be more common at high pressure and high temperature than was previously anticipated.
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6.
  • Colarieti-Tosti, Massimiliano, et al. (författare)
  • On the magnetic anisotropy of Gd metal
  • 2003
  • Ingår i: Physical Review Letters. ; 91, s. 157201
  • Tidskriftsartikel (refereegranskat)abstract
    • Using first-principles theory, we have calculated the energy of Gd as a function of spin direction, , between the c and a axes and found good agreement with experiment for both the total magnetic anisotropy energy and its angular dependence. The calculated low temperature direction of the magnetic moment lies at an angle of 20 to the c axis. The calculated magnetic anisotropy energy of Gd metal is due to a unique mechanism involving a contribution of 7:5 eV from the classical dipoledipoleinteraction between spins plus a contribution of 16 eV due to the spin-orbit interaction of theconduction electrons. The 4f spin polarizes the conduction electrons via exchange interaction, which transfers the magnetic anisotropy of the conduction electrons to the 4f spin.
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7.
  • Colarieti-Tosti, M., et al. (författare)
  • Origin of Magnetic Anisotropy of Gd Metal
  • 2003
  • Ingår i: Physical Review Letters. - 0031-9007. ; 91:15, s. 157201-157204
  • Tidskriftsartikel (refereegranskat)abstract
    • Using first-principles theory, we have calculated the energy of Gd as a function of spin direction, θ, between the c and a axes and found good agreement with experiment for both the total magnetic anisotropy energy and its angular dependence. The calculated low temperature direction of the magnetic moment lies at an angle of 20° to the c axis. The calculated magnetic anisotropy energy of Gd metal is due to a unique mechanism involving a contribution of 7.5  μeV from the classical dipole-dipole interaction between spins plus a contribution of 16  μeV due to the spin-orbit interaction of the conduction electrons. The 4f spin polarizes the conduction electrons via exchange interaction, which transfers the magnetic anisotropy of the conduction electrons to the 4f spin.
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8.
  • da Silva, A. F., et al. (författare)
  • Optical properties of oxide compounds PbO, SnO2 and TiO2
  • 2004
  • Ingår i: Physica Scripta. - 0031-8949. ; T109, s. 180-183
  • Tidskriftsartikel (refereegranskat)abstract
    • The optical properties of the oxide compounds PbO and SnO2 have been investigated experimentally by transmission spectroscopy measurements and theoretically by a full-potential linearized augmented plane wave (FPLAPW) method. The dielectric functions of the rutile TiO2 has also been calculated. The calculated band-gap energies as well as the optical absorption were found to be in a very good qualitatively agreement with the experimental results.
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9.
  • G.E. Grechnev, et al. (författare)
  • Electronic structure and magnetic properties of Lithium manganese spinels
  • 2003
  • Ingår i: J.Magn. Magn. Matt.. ; 258, s. 285
  • Tidskriftsartikel (refereegranskat)abstract
    • Electronic and magnetic structures of the spinel-type lithium–manganese oxides LixMn2O4, x=0,0.5,1, are studied ab initio by employing a full-potential LMTO method. The effect of the orthorhombic distortion on electronic structure and magnetism of LiMn2O4 was investigated, and our calculations do not show a substantial charge ordering at the structural transition from the cubic spinel to the orthorhombic structure.
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