| 1. |
- Kanchana, Venkatakrishnan, et al.
(författare)
-
Density functional study of elastic and vibrational properties of the Heusler-type alloys Fe2VAl and Fe2VGa
- 2009
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 80:12, s. 125108-
-
Tidskriftsartikel (refereegranskat)abstract
- The structural and elastic properties as well as phonon-dispersion relations of the Heusler-type alloys Fe2VAl and Fe2VGa are computed using density functional and density-functional perturbation theory within the generalized-gradient approximation. The calculated equilibrium lattice constants agree well with the experimental values. The elastic constants of Fe2VAl and Fe2VGa are predicted. From the elastic constants the shear modulus, Young's modulus, Poisson's ratio, sound velocities, and Debye temperatures are obtained. By analyzing the ratio between the bulk and shear moduli, we conclude that both Fe2VAl and Fe2VGa are brittle in nature. The computed phonon-dispersion relation shows that both compounds are dynamically stable in the L2(1) structure without any imaginary phonon frequencies. The isomer shifts in Fe in the two compounds are discussed in terms of the Fe s partial density of states, which reveal larger ionicity/less hybridization in Fe2VGa than in Fe2VAl. For the same reason the Cauchy pressure is negative in Fe2VAl but positive in Fe2VGa.
|
|
| 2. |
- Kanchana, Venkatakrishnan, et al.
(författare)
-
Density functional study of the electronic structure and lattice dynamics of SrCl2
- 2010
-
Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 22:44, s. 445402-
-
Tidskriftsartikel (refereegranskat)abstract
- A theoretical study of the structural, electronic, optical and lattice dynamical properties of SrCl2 in the cubic fluorite structure has been performed using first-principles calculations. The calculated ground state and elastic properties are in good agreement with the experiments. The calculated band gap is underestimated within the generalized gradient approximation for the exchange and correlation functional. GW calculations have been performed in order to improve the band gap and good agreement with the experiment is obtained. The phonon dispersion relations are discussed in detail in addition to the ground state and elastic properties. Also, the optical properties are computed with DFT corrected by the GW approximation.
|
|
| 3. |
- Kumar, Ravhi S., et al.
(författare)
-
Pressure-induced valence change in YbAl3 : A combined high-pressure inelastic x-ray scattering and theoretical investigation
- 2008
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 78:7, s. 075117-
-
Tidskriftsartikel (refereegranskat)abstract
- High-resolution x-ray-absorption (XAS) experiments in the partial fluorescence yield mode (PFY) and resonant inelastic x-ray emission (RXES) measurements were performed on the intermediate-valence compound YbAl3 under pressure of up to 38 GPa. The results of the YbAl3 PFY-XAS and RXES studies show that the valence of Yb increases smoothly from 2.75 at ambient pressure to 2.93 at 38 GPa. In situ angle-dispersive synchrotron high-pressure x-ray-diffraction experiments carried out using a diamond cell at room temperature show that the ambient pressure cubic phase is stable up to 40 GPa. The results obtained from self-interaction corrected local spin density-functional calculations to understand the pressure effect on the Yb valence and compressibility are in good agreement with the experimental results.
|
|
| 4. |
- Olsen, J. Staun, et al.
(författare)
-
High-pressure structural behavior of the double perovskite Sr2CrReO6 : an experimental and theoretical study
- 2009
-
Ingår i: High Pressure Research. - : Informa UK Limited. - 0895-7959 .- 1477-2299. ; 29:1, s. 83-86
-
Tidskriftsartikel (refereegranskat)abstract
- The high-pressure structural behavior of Sr2CrReO6 has been studied experimentally using synchrotron radiation and the diamond anvil cell and theoretically using density functional theory. The experimental zero-pressure bulk modulus is B0=1704GPa and the pressure derivative is B0'=4.71.0. These results compare well with the calculated values 172.6GPa and 5.7. A pseudo-cubic unit cell can describe the crystal structure at low pressure, but the tetragonal structure becomes evident at high pressure.
|
|
| 5. |
- Vaitheeswaran, Ganapathy, et al.
(författare)
-
Electronic structure of the ferromagnetic double-perovskites Sr2CrReO6, Sr2CrWO6, and Ba2FeReO6
- 2006
-
Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 29:1, s. 50-53
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the electronic structure of the ferromagnetic double perovskites Sr2CrReO6, Sr2CrWO6 and Ba2FeReO6 by means of a full-potential linear muffin-tin orbital density-functional method. Our scalar-relativistic calculations predict these compounds to be half-metallic with a total magnetic moment of 1, 2, and 3 νB respectively. However, when the spin-orbit coupling is included, the 5d transition Re and W ions exhibit substantial unquenched orbital magnetic moments, resulting in a significant increase of the total magnetic moment. The half-metallic gap turns into a pseudo-gap in Sr 2CrReO6 and Ba2FeReO6 when the spin-orbit coupling is included whereas Sr2CrWO6 remains half-metallic even with spin-orbit coupling. The calculated spin and orbital magnetic moments agrees well with the recent experimental XMCD measurements.
|
|
| 6. |
- Vaitheeswaran, Ganapathy, et al.
(författare)
-
High-pressure structural study of fluoro-perovskite CsCdF3 up to 60 GPa : A combined experimental and theoretical study
- 2010
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:7, s. 075105-
-
Tidskriftsartikel (refereegranskat)abstract
- The structural behavior of CsCdF3 under pressure is investigated by means of theory and experiment. High-pressure powder x-ray diffraction experiments were performed up to a maximum pressure of 60 GPa using synchrotron radiation. The cubic Pm (3) over barm crystal symmetry persists throughout this pressure range. Electronic structure calculations were carried out using the full-potential linear muffin-tin orbital method within the local-density approximation and the generalized gradient approximation for exchange and correlation effects. The calculated ground-state properties-the equilibrium lattice constant, bulk modulus and elastic constants- are in good agreement with experimental results. The calculations reveal that CsCdF3 is an indirect-gap insulator under ambient conditions, with the gap increasing under pressure.
|
|
| 7. |
- Vaitheeswaran, Ganapathy, et al.
(författare)
-
Pseudo-half-metallicity in the double perovskite Sr2CrReO6 from density-functional calculations
- 2005
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 86:3
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of the spintronic material Sr2CrReO6 is studied by means of full-potential linear muffin-tin orbital method. Scalar relativistic calculations predict Sr2CrReO6 to be half-metallic with a magnetic moment of 1 muB. When spin-orbit coupling is included, the half-metallic gap closes into a pseudo-gap, and an unquenched rhenium orbital moment appears, resulting in a significant increase of the total magnetic moment to 1.28 AB. This moment is significantly larger than the experimental moment of 0.9 mu(B). A possible explanation of this discrepancy is that the anti-site disorder in Sr2CrReO6 is significantly larger than hitherto assumed.
|
|
| 8. |
- Winkler, A., et al.
(författare)
-
Magnetism in Re-based ferrimagnetic double perovskites
- 2009
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 11, s. 073047-
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated spin and orbital magnetic moments of the Re 5d ion in the double perovskites A(2)FeReO(6) (A = Ba, Sr, Ca) by x-ray magnetic circular dichroism (XMCD) at the Re L(2,3) edges. In these ferrimagnetic compounds, an unusually large negative spin and positive orbital magnetic moment at the Re atoms was detected. The presence of a finite spin magnetic moment in a 'non-magnetic' double perovskite as observed in the double perovskite Sr(2)ScReO(6) proves that Re has also a small, but finite intrinsic magnetic moment. We further show for the examples of Ba and Ca that the usually neglected alkaline earth ions undoubtedly also contribute to the magnetism in the ferrimagnetic double perovskites.
|
|
