Anisotropic Heat Conduction in Cubic Crystals in the Boundary Scattering Regime

Anisotropic thermal conductivity in uranium dioxide

“…Ballistic phonon transport, which occurs if scattering of phonons in the simulation cell is minimal, is another possible explanation for the anisotropy. This is because under ballistic conditions, thermal conductivity is a fourth rank tensor related to the elastic stiffness tensor and anisotropic thermal conductivity could arise in cubic materials 2,3 . In the MD simulations, ballistic transport is intertwined with the dependence of thermal conductivity on the simulation cell length and scattering by the hot and cold plates.…”

“…Here we show by experiments on single crystals that UO 2 , which crystallizes in the cubic fluorite structure Fm 3m ð Þ, exhibits anisotropic thermal conductivity at temperatures at which ballistic mechanisms are not possible. The anisotropy is rather due to the applied temperature gradient interacting with the electric moments on uranium ions thus affecting the phononspin interactions to slightly break cubic symmetry.…”

A 3D tomographic EBSD analysis of a CVD diamond thin film

“…For instance, in the field of mechanical properties and wear, it was observed that [100]-oriented films exhibit lower roughness and higher wear resistance than those in other crystallographic directions, which renders them suited for tribological applications [13] 1 . 100 -textured films are also ideal for heat-transport applications since the heat conductivity in the crystallographic 100 direction exceeds that in the 111 and 110 directions [9,10]. It has been reported that the dark current of a (001)-oriented diamond film is much lower and more stable than that of a (111)-oriented diamond film [11].…”

“…highest hardness, highest known value of thermal conductivity at 300 K, wide band gap (∼5.5 eV), and broad optical transparency from deep ultraviolet to far infrared), polycrystalline diamond films have attracted increasing attention [1][2][3][4][5]. Since the properties of a diamond crystal depend on the crystallographic direction, it is important to understand the effect of film deposition parameters on the evolution of the crystallographic orientation distribution (texture) and microstructure [6][7][8][9][10][11][12][13][14][15]. For instance, in the field of mechanical properties and wear, it was observed that [100]-oriented films exhibit lower roughness and higher wear resistance than those in other crystallographic directions, which renders them suited for tribological applications [13] 1 .…”

Radial phononic thermal conductance in thin membranes in the Casimir limit: Design guidelines for devices

“…Later, the results was generalized for cases, where the surface scattering was only partially diffusive, 3,8 and for more complex cross-sectional shapes and effects of crystalline symmetries. [9][10][11][12] Note also that the typical Casimir theory does not take into account end effects, in other words effects due to bulk contacts to a rod with a finite length. 13 In experiments in the beam geometry, [14][15][16][17][18][19][20][21] heat flow is indeed uni-directional, and the standard Casimir theory can at least in principle be compared with the experiments.…”