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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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  • 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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5.
  • 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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6.
  • 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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7.
  • 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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8.
  • 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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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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10.
  • Grechnev, Alexei, et al. (författare)
  • Balanced crystal orbital overlap population : a tool for analysing chemical bonds in solids
  • 2003
  • Ingår i: Journal of Physics : Condensed Matter. - 0953-8984. ; 15:45, s. 7751-7761
  • Tidskriftsartikel (refereegranskat)abstract
    • A new tool for analysing theoretically the chemical bonding in solids is proposed. A balanced crystal orbital overlap population (BCOOP) is an energy resolved quantity which is positive for bonding states and negative for antibonding states, hence enabling a distinction between bonding and antibonding contributions to the chemical bond. Unlike the conventional crystal orbital overlap population (COOP), BCOOP handles correctly the situation of crystal orbitals being nearly linear dependent, which is often the case in the solid state. Also, BCOOP is much less basis set dependent than COOP. A BCOOP implementation within the full-potential linear muffin tin orbital method is presented and illustrated for Si, TiC and Ru. Thus, BCOOP is compared to the COOP and crystal orbital Hamilton population (COHP) for systems with chemical bonds ranging from metallic to covalent character.
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