First Principal Study Of Thermal Conductivity Of Cu/Fe/Al And Their Alloy

With the rapid development of science and technology, more new materials areconstantly emerging, while at the same time the research of new thermal conductivematerials and new thermal insulation materials attracts our attention. The determinationof thermal conductivity can be achieved by both experiment and theoretical calculation.But experiment is limited by experimental conditions, and various other nonoperationalfactors. Theoretical calculations can guide the research direction of experiment, and canpresent the variables controlled in experiment. By using the first principles methodbasing on density functional theory, as well as the generalized gradient approximation(GGA) and TM pseudo potential, we studied the internal microscopic mechanism ofheat transfer of metals and alloys, and calculated the phonon spectrum, specific heat,relaxation time, thermal conductivity, etc.In order to reduce the computing time and save computing resources, alloy modelis established by using the method of virtual crystal approximation (VCA). There arethree main interaction processes for electrons in the solids: interactions with phonon,lattice defects and other electrons. As electrons are the identical particles, the collisionsbetween themselves have no effect on heat transfer processes, and here only theinteraction between electrons and phonons is considered. Then, by using the theory oflinear response, we obtained phonon spectrum and specific heat capacity of metals andalloys. Besides, taking advantage of the second order perturbation theory calculations,we can get electron-phonon interaction matrix elements of metals and alloys, thencoupled with Boltzmann theory we got electron thermal conductivity.The study finds that electrons near Fermi level have a great influence on thematerial heat conduction ability, while under the influence of thermal gradient electronsin the valence band can be inspired to the conduction band through a certain path andtake part in heat conduction. For both metal and alloy, constant volume molar specificheat capacity at low temperature follows Debye third power law, while at hightemperature follows Dulong-Petit’s law. Electronic-phonon interaction can limit theelectronic mean free path, and make thermal conductivity unchanged after reaching acertain temperature. When the temperature rises, the lattice contribution to heat transfercannot be ignored, which is the main reason for the deviation between thermal conductivity calculation values and experimental values.