| 1. |
- Belonoshko, Anatoly B., et al.
(författare)
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Quasi ab initio molecular dynamic study of Cu melting
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:6, s. 3838-3844
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the melting of Cu theoretically by means of a molecular dynamic method employing the Sutton-Chen model for the interatomic interaction. This interaction has been fitted to reproduce results from first-principles self-consistent total-energy calculations within the local-density approximation using the full-potential linear-muffin-tin-orbital method for the bcc, fee, hcp, and liquid configurations. No experimental data were used to tune the potential. A large number of properties including equation of state, melting temperature, high-pressure melting curve, change of volume and entropy at melting, liquid structure, diffusion coefficient in liquid, and vacancy formation energy are all in good agreement with experimental data. Inclusion of the full potential energy of a liquid configuration in the fitting procedure is critical for obtaining good agreement with experiment. Different ways to calculate the melting transition are shown to produce very different results. The use of a large number of particles in combination with the solid-liquid interface as an initial configuration in the simulation is essential in order to obtain the correct melting temperatures.
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| 2. |
- Belonoshko, AB, et al.
(författare)
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Quasi ab initio molecular dynamic study of Cu melting
- 2000
-
Ingår i: PHYSICAL REVIEW B. - : AMERICAN PHYSICAL SOC. - 1098-0121. ; 61:6, s. 3838-3844
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the melting of Cu theoretically by means of a molecular dynamic method employing the Sutton-Chen model for the interatomic interaction. This interaction has been fitted to reproduce results from first-principles self-consistent total-
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| 3. |
- Bengone, Oliver, et al.
(författare)
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Electronic structure and transport properties of CrAs/GaAs/CrAs trilayers from first principles theory
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:3
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Tidskriftsartikel (refereegranskat)abstract
- We present a theoretical study of the transport properties of a CrAs/GaAs/CrAs trilayer. The theory was based on a first principles method for calculating the electronic structure, in combination with a Kubo-Landauer approach for calculating the transport properties in a current perpendicular to the plane geometry. We have also investigated the electronic structure and the magnetic properties of this trilayer, with special focus on electronic and magnetic properties at the CrAs/GaAs interface. Finally, we have studied the effects of chemical disorder on the transport properties, in particular the influence of As antisites at both the Cr and Ga sites.
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| 4. |
- Bengone, Oliver, et al.
(författare)
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Origin of the negative giant magnetoresistance effect in Co1-xCrx/Cu/Co (111) trilayers
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 69:9, s. 092406-
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Tidskriftsartikel (refereegranskat)abstract
- We present a theoretical study on Co1-xCrx/Cu/Co (111) trilayers, where a transition from positive to negative giant magnetoresistance effect has been observed experimentally, with increasing thickness of the alloyed layer. The theory, based on a recently implemented conductance calculation, reproduces quantitatively this observation, and the effect is found to be caused by alloying effects, due to a virtual bound Cr d state in the majority spin channel of the Co-Cr layer.
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| 5. |
- Eriksson, Therese, et al.
(författare)
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Magnetic properties of selected Mn-based transition metal compounds with β-Mn structure: Experiments and theory
- 2005
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Ingår i: Physical Review B. ; 72:14, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Two compounds, Mn3CoSi and Mn3CoGe have been synthesized and found to crystallize in the AlAu4 type structure, an ordered form of the β-Mn structure. The magnetic structure and properties have been studied by magnetometry and neutron powder diffraction and the theoretical work is based on first principles total energy calculations. Comparison is made with the magnetic properties of the isostructural compounds Mn3IrGe and Mn3IrSi. The solid solutions Mn3Ir1–yCoySi (0y1) and Mn3CoSi1–xGex (0x1) are also studied. A noncollinear antiferromagnetic structure is experimentally observed for y=0.20 as well as for x=0.50 and 1.0, similar to that of Mn3IrSi and Mn3IrGe, with 120° angles between magnetic moments on a triangular network of Mn atoms, and this finding is corroborated by theoretical calculations. For y=0.80–1.0 a transformation to a new type of magnetic structure takes place. The magnetic transition temperature decreases on decreasing unit cell dimension, with good qualitative agreement with the decay of the calculated interatomic exchange energy. Both theory and experiments find the magnitude of the Mn magnetic moment to decrease on decreasing unit cell volume, the same trend is found in calculations for β-Mn.
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| 6. |
- Fransson, Jonas, et al.
(författare)
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Current-voltage asymmetries and negative differential conductance due to strong electron correlations in double quantum dots
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:8, s. 085301-
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Tidskriftsartikel (refereegranskat)abstract
- A theory for asymmetric current-voltage characteristics, in particular negative differential conductance, for double quantum dots with strongly correlated electron states is formulated. By expressing the double quantum dot in terms of its many-body eigenstates, a diagrammatic technique for Hubbard operator nonequilibrium Green's functions is employed. The Green's function for the double quantum dot is calculated beyond mean field theory, and it is found that the spectral weights of the conductive transitions in the double quantum dot redistribute dynamically (bias voltage dependent). The resulting asymmetric current-voltage characteristics and negative differential conductance is discussed in terms of the relative level spacing in the two quantum dots and the hopping rate between the quantum dots. Numerical results of the current-voltage characteristics are presented and compared to experiments.
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| 7. |
- 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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| 8. |
- Haggstrom, L, et al.
(författare)
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Hyperfine interaction study of (Fe1-xCox)(3)P compounds
- 2000
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Ingår i: PHYSICAL REVIEW B. - : AMERICAN PHYSICAL SOC. - 1098-0121. ; 61:10, s. 6798-6804
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic and ordering properties of (Fe1-xCox)(3)P (x=0, 0.1, 0.2, and 0.33) compounds have been studied by Fe-57 Mossbauer technique. These investigations show that Co preferentially substitutes Fe in two out of three metal sites. Variations of the m
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| 9. |
- Hugosson, Håkan Wilhelm, et al.
(författare)
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Phase stabilities and structural relaxations in substoichiometric TiC1-x
- 2001
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 6316:16, s. 165116-
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Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations have been used to study the effect of vacancies and relaxation around the vacancy sites in substoichiometric TiC1-x. The effect of relaxation on phase stabilities, equilibrium volumes. and electronic structure of the substoichiometric phases was studied using a combined approach of pseudopotential plane wave and full-potential linear muffin-tin orbital methods. A relaxation away from the vacancies was found for the titanium atoms, the magnitude of which increased with vacancy concentration and the inclusion of nearest-neighbor carbon atom relaxation. The inclusion of local relaxations was found to correctly predict the off-stoichiometric equilibrium composition of titanium carbide. The anomalous volume behavior of TiC at small vacancy concentration is explained as an effect of the local relaxation of the atoms surrounding the vacancy sites, but we do not find that the lattice parameter of any of the studied stoichiometries is larger than that of ideal stoichiometric TiC.
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| 10. |
- Kanchana, Venkatakrishnan, et al.
(författare)
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Density functional study of elastic and vibrational properties of the Heusler-type alloys Fe2VAl and Fe2VGa
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 80:12, s. 125108-
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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.
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