| 1. |
- Smirnova, E. A., et al.
(författare)
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Effect of band filling on the pressure-induced structural transition in Mo-Re alloys
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 66:2
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Tidskriftsartikel (refereegranskat)abstract
- We report on a detailed investigation of the combined effect of alloying and compression on the structural stability of random bcc and hcp alloys in the Mo-Re system. We use the linear-muffin-tin-orbital Green's-function method within the coherent potential approximation (LMTO-GF-CPA) and the full-potential linear-muffin-tin-orbital (FP-LMTO) method. For pure Mo we find a bcc to hcp transition pressure to take place at 620 GPa (FP-LMTO) or 730 GPa Mbar (LMTO-GF-CPA). The calculated equation of states for Mo68Re32 alloy is in good agreement with the experimental data, and the calculated bcc-hcp transition pressure is above 400 GPa. This number is much higher than the one anticipated in earlier model calculations. The agreement between the model calculations, ab initio calculations, and the experiment is restored when self-consistent occupation numbers of sp and d electrons are used.
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| 2. |
- Dewhurst, J. K., et al.
(författare)
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Lattice dynamics of solid xenon under pressure
- 2002
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 88:7
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Tidskriftsartikel (refereegranskat)abstract
- We use density-functional perturbation theory to obtain the phonon spectrum of fcc xenon under pressure. Thermodynamic properties obtained within the quasiharmonic approximation are in fair to good agreement with experiment at zero pressure. The transition pressure from the fcc to hcp phase is predicted to occur at 5 GPa. The fcc structure is found to be dynamically stable up to a pressure of 100 GPa, beyond which the phonon modes at the X and L symmetry points soften. We attribute the observed sluggish kinetics of the fcc-hcp transition to the small energy difference between the phases as well as to the high dynamical stability of the fcc phase.
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| 3. |
- Isaeva, E. I., et al.
(författare)
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Ab initio phonon calculations for Ll(2) Ni3Al and B2NiAl
- 2004
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 129:12, s. 809-814
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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.
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| 4. |
- Sharma, P., et al.
(författare)
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Ferromagnetism above room temperature in bulk and transparent thin films of Mn-doped ZnO
- 2003
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 2:10, s. 673-677
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Tidskriftsartikel (refereegranskat)abstract
- The search for ferromagnetism above room temperature in dilute magnetic semiconductors has been intense in recent years. We report the first observations of ferromagnetism above room temperature for dilute (<4 at.%) Mn-doped ZnO. The Mn is found to carry an average magnetic moment of 0.16 μ(B) per ion. Our ab initio calculations find a valance state of Mn2+ and that the magnetic moments are ordered ferromagnetically, consistent with the experimental findings. We have obtained room-temperature ferromagnetic ordering in bulk pellets, in transparent films 2-3 μm thick, and in the powder form of the same material. The unique feature of our sample preparation was the low-temperature processing. When standard high-temperature (T>700degreesC) methods were used, samples were found to exhibit clustering and were not ferromagnetic at room temperature. This capability to fabricate ferromagnetic Mn-doped ZnO semiconductors promises new spintronic devices as well as magneto-optic components.
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