| 1. |
- Bigdeli, Sedigheh, et al.
(författare)
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An insight into using DFT data for Calphad modelling of solid phases in the third generation of Calphad databases, case study for Al
- 2017
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In developing the next generation of Calphad databases, new models are used in which each term contributing to the Gibbs energy has a physical meaning. Harmonic vibrations of atoms are modelled using the Einstein temperature; anharmonic vibrations, electronic and magnetic contributions to the solid phases are represented by specific terms. The two-state model is used for the liquid phase. To continue the development, a new description for unary aluminum is presented in this work. In particular, finite temperature density-functional-theory (DFT) results are used to discuss and suggest the most applicable and physically based model for Calphad assessments of solid phases above the melting point.
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| 2. |
- Rogal, Jutta, et al.
(författare)
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Perspectives on point defect thermodynamics
- 2014
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 251:1, s. 97-129
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Tidskriftsartikel (refereegranskat)abstract
- We review and discuss methods for including the role of point defects in calculations of the free energy, composition and phase stability of elements and compounds. Our principle aim is to explain and to reconcile, with examples, the perspectives on this problem that are often strikingly different between exponents of CALPHAD, and others working in the overlapping fields of physics, chemistry and materials science. Current methodologies described here include the compound energy formalism of CALPHAD, besides the rather different but related canonical and grand-canonical formalisms. We show how the calculation of appropriate defect formation energies should be formulated, how they are included in the different formalisms and in turn how these yield equilibrium defect concentrations and their contribution to free energies and chemical potentials. Furthermore, we briefly review the current state-of-the-art and challenges in determining point defect properties from first-principles calculations as well as from experimental measurements.
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| 3. |
- Stockem, Irina, et al.
(författare)
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Anomalous Phonon Lifetime Shortening in Paramagnetic CrN Caused by Spin-Lattice Coupling: A Combined Spin and Ab Initio Molecular Dynamics Study
- 2018
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 121:12
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Tidskriftsartikel (refereegranskat)abstract
- We study the mutual coupling of spin fluctuations and lattice vibrations in paramagnetic CrN by combining atomistic spin dynamics and ab initio molecular dynamics. The two degrees of freedom are dynamically coupled, leading to nonadiabatic effects. Those effects suppress the phonon lifetimes at low temperature compared to an adiabatic approach. The dynamic coupling identified here provides an explanation for the experimentally observed unexpected temperature dependence of the thermal conductivity of magnetic semiconductors above the magnetic ordering temperature.
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