| 1. |
- Asker Göransson, Christian, et al.
(författare)
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First-principles solution to the problem of Mo lattice stability
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 77:22
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Tidskriftsartikel (refereegranskat)abstract
- The energy differences between the ground state body-centered structure and closed-packed face-centered structure for transition metals in the middle of the series show unusually large disagreements when they are obtained by the thermochemical approach based on the analysis of experimental data or by first-principles electronic structure calculations. Considering a typical example, the lattice stability of Mo, we present a solution to this long-standing problem. We carry out ab initio molecular dynamics simulations for the two phases at high temperature and show that the configurational energy difference approaches the value derived by means of the thermochemical approach. The main contribution to the effect comes from the modification of the canonical band structure due to anharmonic thermal motion at high temperature.
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| 2. |
- Göransson Asker, Christian, et al.
(författare)
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Numerical investigation of the validity of the Slater-Janak transition-state model in metallic systems
- 2005
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 72:13
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Tidskriftsartikel (refereegranskat)abstract
- According to the so-called Janak’s theorem, the eigenstates of the Kohn-Sham Hamiltonian are given by the derivative of the total energy with respect to the occupation numbers of the corresponding one-electron states. The linear dependence of the Kohn-Sham eigenvalues on the occupation numbers is often assumed in order to use the Janak’s theorem in applications, for instance, in calculations of the core-level shifts in materials by means of the Slater-Janak transition state model. In this work first-principles density-functional theory calculations using noninteger occupation numbers for different core states in 24 different random alloy systems were carried out in order to verify the assumptions of linearity. It is found that, to a first approximation, the Kohn-Sham eigenvalues show a linear behavior as a function of the occupation numbers. However, it is also found that deviations from linearity have observable effects on the core-level shifts for some systems. A way to reduce the error with minimal increase of computational efforts is suggested.
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| 3. |
- Music, Denis, et al.
(författare)
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Elastic properties of Fe-Mn random alloys studied by ab initio calculations
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:19
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the influence of the Mn content on the elastic properties of Fe-Mn random alloys (space group of Fm (3) over barm) using ab initio calculations. The magnetic effects in Fe-Mn alloys have a strong influence on the elastic properties, even above the Neel temperature. As the Mn content is increased from 5 to 40 at. %, the C-44 elastic constant is unaffected, while C-11 and C-12 decrease. This behavior can be understood based on the magnetovolume effect which softens the lattice. Since the amplitude of local magnetic moments is less sensitive to volume conserving distortions, the softening is not present during shearing.
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