Electron transport in dense gases: limitations on the Ioffe-Regel and Mott criteria

1986 ◽  
Vol 64 (9) ◽  
pp. 1810-1816 ◽  
Author(s):  
Norman Gee ◽  
Gordon R. Freeman
Keyword(s):  
Carbon Dioxide ◽  
Electron Transport ◽  
Gas Phase ◽  
Free Path ◽  
Mean Free Path ◽  
Repulsive Interaction ◽  
Dense Gases ◽  
Localized State ◽  
The Mean ◽  
Nonspherical Molecules

In the gas phase, the Ioffe–Regel criterion that electron transport becomes modified when the mean free path equals the electron wavelength (L = λ) applies clearly only to helium and hydrogen, which have a net repulsive interaction with electrons. The Mott criterion, that when L = λ/2π the electron is in a localized state, also applies to these two gases. The two criteria are less effective for molecules that have net attractive interactions with the electrons, because the interactions are not simply additive. They are not useful for xenon gas. The criteria are also assessed for: (a) several highly polarizable, spherical and nonspherical molecules; (b) polar molecules; (c) nitrogen and carbon dioxide, which form transient anions.

scholarly journals I. On the applications of the kinetic theory to dense gases

1896 ◽  
Vol 187 ◽  
pp. 1-14
Keyword(s):  
Kinetic Theory ◽  
Free Path ◽  
Relative Motion ◽  
Mean Free Path ◽  
Dense Gases ◽  
Centre Of Gravity ◽  
Mean Pressure ◽  
The Mean

The motion of a great number of elastic spheres, when their aggregate volume does not bear an evanescent ratio to the containing space, has received little attention from writers on the kinetic theory. In what respect, beyond the shortening of the mean free path, will it differ from that of the rare medium usually discussed ? I think that the answer to this question is that there exists in all systems, dense or rare, a tendency for the spheres to move together in masses or streams, and so to diminish the mean pressure per unit of area, and the number of collisions per unit of volume and time. And this tendency has an appreciable influence on the form of the motion as soon as the ratio of the aggregate volume of the spheres to the containing space becomes appreciable. If a part of the system, say n spheres, be at any instant contained in a volume V, they have energy, T r of the motion of their common centre of gravity. And they have energy, T r , of relative motion. As the spheres increase in diameter, the ratio T r /T s , will be found to diminish on average. But the number of collisions per unit of volume and time, given T, or T r , + T s , depends on T r , and therefore diminishes by the diminution of T r .

scholarly journals Ballistic Heat Transport in Nanocomposite: The Role of the Shape and Interconnection of Nanoinclusions

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1982
Author(s):  
Paul Desmarchelier ◽  
Alice Carré ◽  
Konstantinos Termentzidis ◽  
Anne Tanguy
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Free Path ◽  
Mean Free Path ◽  
Strong Increase ◽  
Moderate Increase ◽  
Energy Propagation ◽  
The Mean ◽  
Dynamics Simulations

In this article, the effect on the vibrational and thermal properties of gradually interconnected nanoinclusions embedded in an amorphous silicon matrix is studied using molecular dynamics simulations. The nanoinclusion arrangement ranges from an aligned sphere array to an interconnected mesh of nanowires. Wave-packet simulations scanning different polarizations and frequencies reveal that the interconnection of the nanoinclusions at constant volume fraction induces a strong increase of the mean free path of high frequency phonons, but does not affect the energy diffusivity. The mean free path and energy diffusivity are then used to estimate the thermal conductivity, showing an enhancement of the effective thermal conductivity due to the existence of crystalline structural interconnections. This enhancement is dominated by the ballistic transport of phonons. Equilibrium molecular dynamics simulations confirm the tendency, although less markedly. This leads to the observation that coherent energy propagation with a moderate increase of the thermal conductivity is possible. These findings could be useful for energy harvesting applications, thermal management or for mechanical information processing.

Experiments on the flow of heat in liquid helium below 0.7 °K

1958 ◽  
Vol 246 (1246) ◽  
pp. 390-405 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Liquid Helium ◽  
Free Path ◽  
Empirical Relation ◽  
Mean Free Path ◽  
Series Of Experiments ◽  
The Mean ◽  
Set Up ◽  
Low Pressures ◽  
Measured Thermal Conductivity

A series of experiments has been performed to study the steady flow of heat in liquid helium in tubes of diameter 0.05 to 1.0 cm at temperatures between 0.25 and 0.7 °K. The results are interpreted in terms of the flow of a gas of phonons, in which the mean free path λ varies with temperature, and may be either greater or less than the diameter of the tube d . When λ ≫ d the flow is limited by the scattering of the phonons at the walls, and the effect of the surface has been studied, but when λ ≪ d viscous flow is set up in which the measured thermal conductivity is increased above that for wall scattering. This behaviour is very similar to that observed in the flow of gases at low pressures, and by applying kinetic theory to the problem it can be shown that the mean free path of the phonons characterizing viscosity can be expressed by the empirical relation λ = 3.8 x 10 -3 T -4.3 cm. This result is inconsistent with the temperature dependence of λ as T -9 predicted theoretically by Landau & Khalatnikov (1949).

Light scattering by phonons in the presence of a heat flow

1968 ◽  
Vol 46 (24) ◽  
pp. 2843-2845 ◽  
Author(s):  
Allan Griffin
Keyword(s):  
Light Scattering ◽  
Heat Flow ◽  
Temperature Gradient ◽  
Free Path ◽  
Mean Free Path ◽  
Photon Scattering ◽  
The Mean ◽  
Anti Stokes

If the temperature in an insulating crystal decreases in the z-direction, there are more phonons with momentum qz > 0 than with qz < 0. The resulting difference between the Stokes and anti-Stokes Brillouin intensities is proportional to the mean free path of the phonon involved and to the temperature gradient. The effect should be observable by either neutron or photon scattering.

Role of neutral-particle bombardment in dust–dust interactions in plasmas

2001 ◽  
Vol 65 (4) ◽  
pp. 257-272 ◽  
Author(s):  
Ya. K. KHODATAEV ◽  
G. E. MORFILL ◽  
V. N. TSYTOVICH
Keyword(s):  
Free Path ◽  
Particle Bombardment ◽  
Neutral Particle ◽  
Mean Free Path ◽  
Dust Particles ◽  
Neutral Particles ◽  
Additional Force ◽  
Numerical Coefficient ◽  
The Mean

It is shown that the interaction of dust with neutral plasma particles can lead to attractive forces between dust particles, both in the case where the distance between dust particles is less than the mean free path of neutral particles and in the case where it is greater. The expressions for attractive forces differs in the two limits only by a numerical coefficient. The additional force of dust interaction is found to be due to the neutrals created by recombination of charged plasma particles on the surface of dust particles. The influence of radiative dust cooling on dust–dust interaction is considered.

Sign in / Sign up

Export Citation Format

Share Document