Direct method for calculating temperature-dependent transport properties (original) (raw)
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Physical Review B
An approach previously developed for the calculation of transport coefficients via the Mott relations is applied to the calculation of finite temperature transport properties of disordered alloys-electrical resistivity and the electronic part of thermal conductivity. The coherent potential approximation (CPA) is used to treat chemical disorder as well as other sources of electron scattering, i.e. temperature induced magnetic moment fluctuations and lattice vibrations via the alloy analogy model. This approach, which treats all forms of disorder on an equal first principles footing, is applied to the calculation of transport properties of a series of face-centered crystal cubic (fcc) concentrated solid solutions of the 3d-transition metals Ni, Fe, Co and Cr. For the nonmagnetic alloys, Ni 0.8 Cr 0.2 , and Ni 0.33 Co 0.33 Cr 0.3 the combined effects of chemical disorder and electron-lattice vibrations scattering result in a monotonic increase in the resistivity as a function of temperature from an already large, T=0, residual resistivity. For magnetic Ni 0.5 Co 0.5 , Ni 0.5 Fe 0.5 , Ni 0.33 Fe 0.33 Co 0.33 , whose residual resistivity is small, additional electron scattering from temperature induced magnetic moment fluctuations results in a further rapid increase of the resistivity as a function of temperature. The electronic part of the thermal conductivity in nonmagnetic, Ni 0.8 Cr 0.2 , and Ni 0.33 Co 0.33 Cr 0.33 , monotonically increases with temperature. This behavior is a result of the competition between a reduction in the conductivity due to electron-lattice vibrations scattering and temperature induced increase in the number of carriers. In the magnetic alloys, electron scattering from magnetic fluctuations leads to an initial rapid decrease in thermal conductivity until this is overcome by an increasing number of carriers at temperatures slightly below the Curie temperature. Similar to the resistivity above T C , the electronic part of the thermal conductivities are close to each other in all alloys studied.
Temperature dependent electronic transport in concentrated solid solutions of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">mml:mrowmml:mn3mml:mid -transition metals Ni, Fe, Co and Cr from first principles
Physical review, 2018
An approach previously developed for the calculation of transport coefficients via the Mott relations is applied to the calculation of finite temperature transport properties of disordered alloys-electrical resistivity and the electronic part of thermal conductivity. The coherent potential approximation (CPA) is used to treat chemical disorder as well as other sources of electron scattering, i.e. temperature induced magnetic moment fluctuations and lattice vibrations via the alloy analogy model. This approach, which treats all forms of disorder on an equal first principles footing, is applied to the calculation of transport properties of a series of face-centered crystal cubic (fcc) concentrated solid solutions of the 3d-transition metals Ni, Fe, Co and Cr. For the nonmagnetic alloys, Ni 0.8 Cr 0.2 , and Ni 0.33 Co 0.33 Cr 0.3 the combined effects of chemical disorder and electron-lattice vibrations scattering result in a monotonic increase in the resistivity as a function of temperature from an already large, T=0, residual resistivity. For magnetic Ni 0.5 Co 0.5 , Ni 0.5 Fe 0.5 , Ni 0.33 Fe 0.33 Co 0.33 , whose residual resistivity is small, additional electron scattering from temperature induced magnetic moment fluctuations results in a further rapid increase of the resistivity as a function of temperature. The electronic part of the thermal conductivity in nonmagnetic, Ni 0.8 Cr 0.2 , and Ni 0.33 Co 0.33 Cr 0.33 , monotonically increases with temperature. This behavior is a result of the competition between a reduction in the conductivity due to electron-lattice vibrations scattering and temperature induced increase in the number of carriers. In the magnetic alloys, electron scattering from magnetic fluctuations leads to an initial rapid decrease in thermal conductivity until this is overcome by an increasing number of carriers at temperatures slightly below the Curie temperature. Similar to the resistivity above T C , the electronic part of the thermal conductivities are close to each other in all alloys studied.
Calculations of spin-disorder resistivity from first principles
2007
Spin-disorder resistivity of Fe and Ni is studied using the noncollinear density functional theory. The Landauer conductance is averaged over random disorder configurations and fitted to Ohm's law. The distribution function is approximated by the mean-field theory. The dependence of spin-disorder resistivity on magnetization in Fe is found to be in excellent agreement with the results for the isotropic s-d model. In the fully disordered state, spin-disorder resistivity for Fe is close to experiment, while for fcc Ni it exceeds the experimental value by a factor of 2.3. This result indicates strong magnetic short-range order in Ni at the Curie temperature. We suggest that the analysis of calculated and measured spin-disorder resistivity provides a powerful method to extract information on the temperature dependence of the magnetic short-range order parameter in ferromagnetic metals.
The Effect of Disorder on Lattice Thermal Transport in Solid Solution Alloys
Bulletin of the American Physical Society, 2016
been recently observed. The strongly decreased damage retention in these highly disordered materials is attributed to severe disruption of the pathways of energy dissipation away from atomic displacement cascades. Because the energy of an irradiating ion is primarily deposited into the lattice degrees of freedom, it is the lattice thermal conductivity that is most important to the dissipation of heat from damage events. Here we report measurements of phonon linewidths in NiCo, NiFe, and NiFeCoCr using inelastic neutron and X-ray scattering, showing a dramatic increase in phonon linewidth by a factor of 4 with increasing disorder. Measured phonon linewidths are shown in comparison to theoretical phonon linewidths originating from disorder calculated using the itinerant coherent potential approximation (I-CPA). Lattice thermal conductivity is calculated from the phonon properties, and compared to measurements of bulk thermal and electrical properties. The impact of the observed decrease in lattice thermal conductivity on damage resistance is discussed.
Impact of finite temperatures on the transport properties of Gd from first principles
Physical Review B, 2017
Finite temperature effects have a pronounced impact on the transport properties of solids. In magnetic systems, besides the scattering of conduction electrons by impurities and phonons, an additional scattering source coming from the magnetic degrees of freedom must be taken into account. A first-principle scheme which treats all these scattering effects on equal footing was recently suggested within the framework of the multiple scattering formalism. Employing the alloy analogy model treated by means of the CPA, thermal lattice vibrations and spin fluctuations are effectively taken into account. In the present work the temperature dependence of the longitudinal resistivity and the anomalous Hall effect in the strongly correlated metal Gd is considered. The comparison with experiments demonstrates that the proposed numerical scheme does provide an adequate description of the electronic transport at finite temperatures.
The calculation of transport properties and density of states of disordered solids
European Physical Journal B, 1985
A computational method is presented for the calculation of the conductivity tensor and the density of states of disordered solids. This is a more general and detailed discussion of an algorithm which has been applied to d.c. and a.c. conductivity, Hall effect and density of states of various systems.
Journal of Experimental and Theoretical Physics, 2005
We consider the singular electron-electron interaction corrections to the transport coefficients in disordered metals to test the validity of the Wiedemann-Franz law. We develop a local, quantum kinetic equation approach in which the charge and energy conservation laws are explicitly obeyed. To obtain the local description, we introduce bosonic distribution functions for the neutral, lowenergy collective modes (electron-hole pairs). The resulting system of kinetic equations enables us to distinguish between the different physical processes involved in the charge and energy transport: elastic electron scattering affects both, while the inelastic processes influence only the latter. Moreover, the neutral bosons, though incapable of transporting charge, contribute significantly to the energy transport. In our approach we calculate on equal footing the electrical and thermal conductivities and the specific heat in any dimension. We found that the Wiedemann-Franz law is always violated by the interaction corrections; the violation is larger for one-and two-dimensional systems in the diffusive regime T τ ≪h and it is due to the energy transported by the neutral bosons. For two-dimensional systems in the quasi-ballistic regime T τ ≫h the inelastic scattering of the electron on the bosons also contributes to the violation.
Monte Carlo study of the spin transport in magnetic materials
Computational Materials Science, 2010
The resistivity in magnetic materials has been theoretically shown to depend on the spin-spin correlation function which in turn depends on the magnetic-field, the density of conduction electron, the magnetic ordering stability, etc. However, these theories involved a lot of approximations, so their validity remained to be confirmed. The purpose of this work is to show by newly improved extensive Monte Carlo (MC) simulation the resistivity of the spin resistivity from low-T ordered phase to high-T paramagnetic phase in ferromagnetic and antiferromagnetic films. We take into account the interaction between the itinerant spins and the localized lattice spins as well as the interaction between itinerant spins themselves. We show that in ferromagnets the resistivity shows a sharp peak at the magnetic phase transition in agreement with previous theories in spite of their numerous approximations. Resistivity in antiferromagnets on the other hand shows no peak for the SC, BCC and diamond lattices. Discussion on the origin of these resistivity behaviors is given.
Thermal Conductivity in Ferromagnetic Materials using Molecular Dynamics Simulations
2021
Insulating non-magnetic solids conduct heat through the lattice vibrations, also colloquially known as phonons. In magnetic solids, additional channels for heat transport are available through the interaction of magnetic moments. Opposing this interaction are lattice vibrations which couple with the magnetic moments on the atoms and thus provide additional resistance to heat flow. There is currently no complete understanding of the magnitudes of these contributions, and the overall effect of the magnetic contribution is largely unknown. Using a combination of spin dynamics and molecular dynamics simulations, we modeled the contribution of the magnetic subsystem to the lattice thermal conductivity across ferromagnetic to paramagnetic transitions in elemental Iron. Application of the approach to the anti-ferromagnetic materials is discussed for the example of the technologically important material, uranium dioxide. Introduction Pressed uranium dioxide (UO2) pellets are used in the nuc...
The Inhomogeneous Transport Regime and Metal-Nonmetal Transitions in Disordered Material
Le Journal de Physique Colloques
Rbum6.-Nous avanqons une representation physique pour les changements apparemment continus dans la structure electronique et les proprietks de transport, observes au cours des transitions metal-non metal, se produisant dans les nombreux materiaux dksordonnes. Des deformations structurales ayant pour origine des fluctuations de densite, des modifications de liaisons, la formation de composes ou d'agglomerats, peuvent se traduire par une non-homogen6it6 microscopique locale dans la structure Clectronique de tels mattriaux. Quand la courte distance de correlationde Debyepour les fluctuations est suffisamment grande, celles-ci peuvent Ctre considerees comme statistiquement indkpendantes. De plus en prenant les phases electroniques au hasard, a 1'6chelle de variation de la configuration locale, on peut definir une structure 6lectronique locale et des fonctions locales approprikes. Finalement quand les effets quantiques produits par effet tunnel, et quand les corrections d'energie cinetique sont petits, I'image semi-classique est applicable. En consequence nous pouvons considerer un regiment de transport non homogene dans lequel des effets de percolation se traduisent par un changement continu des proprietes de transport. Une version generaliske de la thCorie du milieu effectif pour la conductivite thermique, l'effet Hall, et le pouvoir thermoelectrique, a Bt B utilisCe pour analyser plusieurs classes de materiaux subissant une transition continue metal-non metal. Une application detaillee de la thkorie est presentee pour des systemes a un constituant tels que Hg liquide ktendu et Te liquide, ainsi que pour des systemes binaires tels que alliages mktalliques et solutions metal-ammoniaque.