Thermal Conductivity - Physical Origins

Physical Origins

Heat flux is exceedingly difficult to control and isolate in a laboratory setting. Thus at the atomic level, there are no simple, correct expressions for thermal conductivity. Atomically, the thermal conductivity of a system is determined by how atoms composing the system interact. There are two different approaches for calculating the thermal conductivity of a system.

  • The first approach employs the Green-Kubo relations. Although this employs analytic expressions which in principle can be solved, calculating the thermal conductivity of a dense fluid or solid using this relation requires the use of molecular dynamics computer simulation.
  • The second approach is based upon the relaxation time approach. Due to the anharmonicity within the crystal potential, the phonons in the system are known to scatter. There are three main mechanisms for scattering:
    • Boundary scattering, a phonon hitting the boundary of a system;
    • Mass defect scattering, a phonon hitting an impurity within the system and scattering;
    • Phonon-phonon scattering, a phonon breaking into two lower energy phonons or a phonon colliding with another phonon and merging into one higher energy phonon.

Read more about this topic:  Thermal Conductivity

Famous quotes containing the words physical and/or origins:

    The peace loving nations must make a concerted effort in opposition to those violations of treaties and those ignorings of humane instincts which today are creating a state of international anarchy and instability from which there is no escape through mere isolation or neutrality.... When an epidemic of physical disease starts to spread, the community approves and joins in a quarantine of the patients in order to protect the health of the community against the spread of the disease.
    Franklin D. Roosevelt (1882–1945)

    Grown onto every inch of plate, except
    Where the hinges let it move, were living things,
    Barnacles, mussels, water weeds—and one
    Blue bit of polished glass, glued there by time:
    The origins of art.
    Howard Moss (b. 1922)