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- Belonoshko, Anatoly B., et al.
(författare)
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Molecular dynamics simulation of the structure of yttria Y2O3 phases using pairwise interactions
- 2001
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 6418:18
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the structure of yttria (Y2O3) by means of ab initio and molecular dynamics methods. The suggested simple model for the interatomic interaction is shown to produce reasonable results at moderate pressures for a wide range of temperatures. The calculated x-ray structure factor is in good agreement with experimental data obtained by the x-ray levitation technique at the temperature of 2526 K. The quality of the agreement decreases with increasing temperature. We demonstrate that it is not necessary to assume nonstoichiometry of liquid yttria, as was done in a recent publication, to obtain agreement with experiment. The structure of liquid yttria can be considered as a mixture of 4- and 6-coordinated Y atoms. We also show the possibility of a light amorphous yttria phase, which possibly can be obtained by quenching from a vapor instead of conventional amorphous yttria quenched from a liquid.
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| 2. |
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| 3. |
- G.E. Grechnev,, et al.
(författare)
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Electronic structure and magnetic properties of Lithium manganese spinels
- 2003
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Ingår i: J.Magn. Magn. Matt.. ; 258, s. 287-289
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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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| 4. |
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| 5. |
- Grechnev, G. E., et al.
(författare)
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Electronic structure, magnetic, and cohesive properties of LixMn2O4 : Theory
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 65:17
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Tidskriftsartikel (refereegranskat)abstract
- The volume dependent electronic structure of the spinel-type lithium manganese oxides LixMn2O4, x=0,0.5,1, is studied ab initio by employing a full-potential electronic structure method. The electronic structure, total energies, open-circuit voltage, and magnetic moments were obtained for various spin configurations of LixMn2O4 in the cubic spinel structure and the low-temperature orthorhombic structure. The effect of magnetic ordering on the band structure and structural stability has been investigated and an antiferromagnetic ordering proved to be the ground state of the LixMn2O4 spinels. Our calculations show that the manganese majority t(2g) d band is filled for all LixMn2O4 compounds studied, and the filling of the minority t(2g) band is expected in the lithiation process. The lithium intercalation potential, bulk modulus, magnetic moments, and optical properties are calculated within the itinerant band approach and are found to be in good agreement with available experimental data, indicating, that the density-functional theory provides reliable electronic structure of the LixMn2O4 system. 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, as proposed earlier. Instead, the low-temperature orthorhombic structure is found to possess the lowest energy via a Jahn-Teller distortion driven by the d band.
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| 6. |
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| 7. |
- Grechnev, G. E., et al.
(författare)
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Magnetic susceptibility of hcp iron and the seismic anisotropy of Earth's inner core
- 2003
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Ingår i: PHYSICAL REVIEW B. - 1098-0121. ; 68:6, s. 064414-
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Tidskriftsartikel (refereegranskat)abstract
- The seismic anisotropy of the Earth's core is believed to be due to a preferred orientation of hexagonal close packed (hcp) iron crystals that constitute the dominating element in the inner core. In this connection, the magnetic properties of the hcp iron in an external magnetic field are very interesting and are studied here by employing an ab initio full-potential linear muffin tin orbital method. By this means the magnetic susceptibility chi of hcp iron and its anisotropy energy for pressures and temperatures corresponding to the Earth's inner core conditions have been evaluated in the framework of the local spin density approximation. The accuracy of this method has been validated by calculating the anisotropic susceptibility of paramagnetic transition metals that form in the hcp crystal structure at ambient conditions. Our calculations demonstrate that for hcp iron the anisotropy of chi is dependent on the c/a ratio. In conjunction with recent data on the c/a ratio and elastic constants of hcp iron, the magnetic anisotropy can explain the seismic anisotropy of the Earth's inner core.
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| 8. |
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| 9. |
- Gutierrez, G., et al.
(författare)
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Structural properties of liquid Al2O3 : A molecular dynamics study
- 2000
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1063-651X .- 1095-3787. ; 61:3, s. 2723-2729
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics (MD) simulations of liquid aluminum oxide (Al2O3) were carried out on a system with up to 1800 particles, using a pairwise potential. All simulations were done in the microcanonical ensemble, for two densities, 3.0 and 3.175 g/cm(3), at temperatures of 2200, 2600, and 3000 K. A detailed analysis of the interatomic distances, given by the partial pair-distribution functions and the bond-angles distribution, reveals that in the liquid state there is st short range order dominated by a somewhat distorted (AlO4)(5-) tetrahedron, in agreement with recent experimental measurements. This conclusion is supported by the distribution of nearest-neighbor coordinations, where more than 60% of Al atoms have four O as nearest neighbors. This finding does not change over the explored temperature range. Because of the presence of twofold rings, the connectivity of (AlO4)(5-) units consists of corner, edge, and face sharing tetrahedra. Based in this structural information, i.e., bond lengths, coordination numbers, bond-angle distributions, and ring statistics, our MD simulation allows us to put forward a possible structure of liquid Al2O3.
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| 10. |
- Gutierrez, G, et al.
(författare)
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Structural properties of liquid Al2O3: A molecular dynamics study
- 2000
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Ingår i: PHYSICAL REVIEW E. - : AMERICAN PHYSICAL SOC. - 1063-651X. ; 61:3, s. 2723-2729
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics (MD) simulations of liquid aluminum oxide (Al2O3) were carried out on a system with up to 1800 particles, using a pairwise potential. All simulations were done in the microcanonical ensemble, for two densities, 3.0 and 3.175 g/cm(3), at
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