What is thermal conductivity phonon?

What is thermal conductivity phonon?

Thermal conductivity. κ is defined as the energy transmitted per unit time across unit area per unit temperature. gradient. Dependence of κ on dT/dx implies that the thermal energy transfer is a random process involving scattering – introduces mean free path of phonons in the problem.

What is phonon dispersion?

The phonon dispersion relations are defined as the k dependence of the frequencies, ω k , j , of the normal modes for all branches j and selected directions in the crystal (Figure 1). The number of phonon branches, j = 1 , 2 , … , 3 r , is equal to the number of degrees of freedom in the primitive unit cell.

What is thermal conductivity of a material?

Thermal conductivity can be defined as the rate at which heat is transferred by conduction through a unit cross-section area of a material, when a temperature gradient exits perpendicular to the area.

What is lattice thermal conductivity?

Lattice thermal conductivity (κ) is one of the most important thermoelectric parameters in determining the energy conversion efficiency of thermoelectric materials. However, thermal conductivity calculations are time-consuming in solving the Boltzmann transport equation or performing the molecular dynamic simulations.

What is phonon heat capacity?

Unlike photons, there are three polarizations for each propagation direction (not two), and k cannot take on arbitrary values—it can only take on values in the first Brillouin zone. Phonon heat capacity. Heat capacity is a materials property which converts absorbed energy into an increase in temperature.

What is the accumulative thermal conductivity of phonons?

The accumulative thermal conductivity is usually used to resolve the MFPs of dominant heat-carrying phonons, which is defined as 156, 157:

How is the energy of a phonon related to its temperature?

We make a relaxation time kind of approximation: the energy contributed by a phonon at a point is decided by where it has had its last collision. So phonons coming from the high temperature end bring more energy than those coming from the low temperature end.

What are some of the best books on phonon wave heat conduction?

Phys. Rev. B 61, 3091 (2000). 78. Chen, G. Phonon wave heat conduction in thin films and superlattices. J. Heat. Transf. 121, 945–953 (1999). 79. Yang, B. & Chen, G. Partially coherent phonon heat conduction in superlattices. Phys. Rev. B 67, 195311 (2003). 80. Maire, J. et al. Heat conduction tuning by wave nature of phonons. Sci.

What is the effect of four-phonon scattering on thermal conductivity of solids?

Ravichandran, N. K. & Broido, D. Phonon-phonon interactions in strongly bonded solids: selection rules and higher-order processes. Phys. Rev. 10, 021063 (2020). 33. Feng, T., Lindsay, L. & Ruan, X. Four-phonon scattering significantly reduces intrinsic thermal conductivity of solids.