| 1. |
|
|
| 2. |
- Landa, A., et al.
(författare)
-
Density-functional study of Zr-based actinide alloys
- 2009
-
Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 385:1, s. 68-71
-
Tidskriftsartikel (refereegranskat)abstract
- Density-functional formalism is applied to study the phase equilibria in the U-Zr system. The obtained ground-state properties of the gamma (bcc) and delta (02) phases are in good agreement with experimental data. The decomposition curve for the gamma-based U-Zr solutions is calculated. We argue that stabilization of the delta-UZr2 phase relative to the alpha-Zr (hcp) structure is due to an increase of the Zr d-band occupancy that occurs when U is alloyed with Zr.
|
|
| 3. |
- Landa, A., et al.
(författare)
-
Density-functional study of Zr-based actinide alloys : 2. U-Pu-Zr system
- 2009
-
Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 393:1, s. 141-145
-
Tidskriftsartikel (refereegranskat)abstract
- Density-functional theory, previously used to describe phase equilibria in the U-Zr alloys [A. Landa, P. Soderlind, P.E.A. Turchi, L. Vitos, A. Ruban, J. Nucl. Mater. 385 (2009) 68[, is applied to study ground-state properties of the bcc U-Pu-Zr solid solutions. Calculated heats of formation of the Pu-U and Pu-Zr alloys are in a good agreement with CALPHAD assessments. We found that account for spin-orbit coupling is important for successful description of Pu-containing alloys.
|
|
| 4. |
|
|
| 5. |
- Dalén, Love, et al.
(författare)
-
Population structure in a critically endangered arctic fox population : does genetics matter?
- 2006
-
Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 15:10, s. 2809-2819
-
Tidskriftsartikel (refereegranskat)abstract
- The arctic fox (Alopex lagopus) in Scandinavia is classified as critically endangered after having gone through a severe decline in population size in the beginning of the 20th century, from which it has failed to recover despite more than 65 years of protection. Arctic foxes have a high dispersal rate and often disperse over long distances, suggesting that there was probably little population differentiation within Scandinavia prior to the bottleneck. It is, however, possible that the recent decline in population size has led to a decrease in dispersal and an increase in population fragmentation. To examine this, we used 10 microsatellite loci to analyse genetic variation in 150 arctic foxes from Scandinavia and Russia. The results showed that the arctic fox in Scandinavia presently is subdivided into four populations, and that the Kola Peninsula and northwest Russia together form a large fifth population. Current dispersal between the populations seemed to be very low, but genetic variation within them was relatively high. This and the relative F-ST values among the populations are consistent with a model of recent fragmentation within Scandinavia. Since the amount of genetic variation is high within the populations, but the populations are small and isolated, demographic stochasticity seems to pose a higher threat to the populations' persistence than inbreeding depression and low genetic variation.
|
|
| 6. |
|
|
| 7. |
- Landa, A., et al.
(författare)
-
Ab initio calculations of elastic constants of the bcc V-Nb system at high pressures
- 2006
-
Ingår i: Journal of Physics and Chemistry of Solids. - : Elsevier BV. - 0022-3697 .- 1879-2553. ; 67:10-sep, s. 2056-2064
-
Tidskriftsartikel (refereegranskat)abstract
- First-principles total energy calculation based on the exact muffin-tin orbital and full-potential linear muffin-tin orbital methods were used to calculate the equation of state and shear elastic constants of bcc V, Nb, and the V95Nb05 disordered alloy as a function of pressure up to 6 Mbar. We found a mechanical instability in C-44 and a corresponding softening in C at pressures similar to 2 Mbar for V. Both shear elastic constants show softening at pressures similar to 0.5 Mbar for Nb. Substitution of 5 at% of V with Nb removes the instability of V with respect to trigonal distortions in the vicinity of 2 Mbar pressure, but still leaves the softening of C-44 in this pressure region. We argue that the pressure-induced shear instability (softening) of V (Nb) originates from the electronic system and can be explained by a combination of the Fermi surface nesting, electronic topological transition, and band Jahn-Teller effect.
|
|
| 8. |
- Landa, A., et al.
(författare)
-
Fermi surface nesting and pre-martensitic softening in V and Nb at high pressures
- 2006
-
Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 18:22, s. 5079-5085
-
Tidskriftsartikel (refereegranskat)abstract
- First-principles total-energy calculations were performed for the trigonal shear elastic constant (C-44) of body-centred cubic (bcc) V and Nb. A mechanical instability in C44 is found for V at pressures of similar to 2 Mbar which also shows a softening in Nb at pressures of similar to 0.5 Mbar. We argue that the pressure-induced shear instability (softening) of V (Nb) is due to the intra-band nesting of the Fermi surface.
|
|
| 9. |
- Landa, A., et al.
(författare)
-
Stability in bcc Transition Metals : Madelung and Band-Energy Effects due to Alloying
- 2009
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 103:23
-
Tidskriftsartikel (refereegranskat)abstract
- The phase stability of group VB (V, Nb, and Ta) transition metals is explored by first-principles electronic-structure calculations. Alloying with a small amount of a neighboring metal can either stabilize or destabilize the body-centered-cubic phase relative to low-symmetry rhombohedral phases. We show that band-structure effects determine phase stability when a particular group VB metal is alloyed with its nearest neighbors within the same d-transition series. In this case, the neighbor with less (to the left) and more (to the right) d electrons destabilize and stabilize bcc, respectively. When alloying with neighbors of higher d-transition series, electrostatic Madelung energy dominates and stabilizes the body-centered-cubic phase. This surprising prediction invalidates current understanding of simple d-electron bonding that dictates high-symmetry cubic and hexagonal phases.
|
|
