Maxwell-Boltzmann distribution for transport equations

AI Thread Summary
The discussion focuses on calculating transport coefficients using the Maxwell-Boltzmann distribution, specifically for electrical conductivity. The user is uncertain about the correct distribution function to apply, emphasizing the need for a state-based distribution rather than velocity or energy distributions. They reference the normalized Maxwell-Boltzmann distribution and express confusion regarding the normalization constant and its implications for dimensions. Key points include the relationship between the distribution function and the Drude formula for conductivity, as well as the significance of the mean values in the normalization factor. Clarification on the normalization constant and its components is sought to ensure accurate calculations.
Denver Dang
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I have to calculate the transport coefficients for the Maxwell-Boltzmann distribution. But I'm not sure what distribution I have to use.
As far as I know it should not be the MB distribution for v-space (Velocity) or E-axis (Energy), since that will get me the wrong dimensions in the end. I have to use the distribution per state.

But I'm not sure how this looks. The integral I have to solve, for me getting the electrical conductivity (1st transport coefficient) I need, is given by:

{{\mathcal{L}}^{\,\left( 0 \right)}}={{\left( \frac{2m}{{{\hbar }^{2}}} \right)}^{3/2}}\frac{{{e}^{2}}\tau }{{{\pi }^{2}}m}\int{\left( -\frac{\partial {{f}_{MB}}}{\partial \varepsilon } \right)}\,{{\varepsilon }^{3/2}}d\varepsilon,

at least, again, when trying to calculate the electrical conductivity, which in the end should end up being Drudes formula \sigma =\frac{n{{e}^{2}}\tau }{m}.

So basically, not hard. But I have to get the distribution function right.

As far as I know the MB-distribution is given by:

{{f}_{MB}}\left( \varepsilon \right)=C{{e}^{-\varepsilon /{{k}_{B}}T}},

where C is what I need to figure out, since that will determine the dimensions of my coefficients.

According to my book the normalized MB distribution function is:

\bar{n}=\frac{{\bar{N}}}{{{Z}_{1}}\left( T,V \right)}{{e}^{-\varepsilon /{{k}_{B}}T}},

where:

\frac{{{Z}_{1}}\left( T,V \right)}{{\bar{N}}}=\frac{V}{{\bar{N}}}\left( \frac{2\pi m{{k}_{B}}T}{{{h}^{2}}} \right){{Z}_{\operatorname{int}}}\left( T \right),

and {{Z}_{\operatorname{int}}}\left( T \right) = 1 in my case.

But I'm not quite sure how to about this? As far as I can see, it's not just inserting the reversed term of this in C - at least not from what I can see. Maybe it's the V/N I'm not sure about.

So, anyone who can give me a clue, or...?
 
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Your normalization factor should be :

\frac{{{Z}_{1}}\left( T,V \right)}{{\bar{N}}}=\frac{V}{{\bar{N}}}\left( \frac{2\pi m{{k}_{B}}T}{{{h}^{2}}} \right)^{3/2}


The n in the drude law is the number density. i.e. the number of electrons per unit volume. In your normalization constant what is \bar{n}, \bar{N} ? :wink:
 
The bar over n and N means the "mean" of whatever it is...

But do I know what this is ?
Or at least V/N, or...?
 
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