Introduction level Solid State - Mean free time/path & lattice spacing

In summary, the conversation revolves around calculating the average time and mean free path of electrons in silver, assuming the classical free electron gas model. The person is stuck on calculating the lattice spacing and is seeking help from others. They are given a method to estimate the lattice spacing using the density and mass of a silver nucleus, and the conversation ends with a comparison of the estimated lattice spacing to the actual values found online.
  • #1
Yosty22
185
4

Homework Statement



Silver has a density of 10.5E3 kg/m3 and a resistivity of 1.6E-8 Ω*m at room temperature. On the basis of the classical free electron gas model, and assuming that each silver atom contributes one electron to the electron gas, calculate the average time, Tau, between collisions of the electrons. Calculate the mean free path from tau and the electron's thermal velocity. How does the mean free path compare to the lattice spacing?

Homework Equations





The Attempt at a Solution



I was able to do all of the calculations fairly easily, but I'm stuck on the lattice spacing. My professor told us that we could just look up the lattice spacing of a silver crystal for the sake of comparison, but I was unable to find it online. As my class just has a brief one or two chapter long introduction to solid state physics, we haven't touched on how to calculate this and I could not find it in my textbook. Since I cannot find the lattice spacing of a silver crystal online, I was just wondering if anybody knows how I can calculate the lattice spacing from the information that I am given in this problem. Is this sufficient information to calculate it myself without having to look it up? I haven't found anything in my textbook, but as this is just a few-chapter introduction to the basics of solid state physics, I was wondering if there is any way to calculate this that my book may not mention with such a brief introduction?

Thanks in advanced.
 
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  • #2
Well, to get an estimate for lattice spacing, you could probably use the density of silver, and the mass of a silver nucleus right? Most of the mass of silver is in the nucleus, so from the density ρ we can get the rough number density of nucleons n=ρ/m (where m is the mass of one silver nucleus) and from n, you can deduce a rough lattice spacing from d~(1/n)^(1/3).

Using this method I get an answer of ~2.5 angstroms. Wolfram alpha gives the silver lattice spacings of ~2.4 angstroms, 2 anstroms, and 1.2 angstroms. So it seems like we were close (to one of them lol)...
 

Related to Introduction level Solid State - Mean free time/path & lattice spacing

1. What is the mean free time or mean free path in solid state materials?

The mean free time or mean free path in solid state materials refers to the average time or distance between collisions of particles (such as electrons) within the material. It is a measure of how often and how far particles can move before being scattered by impurities, defects, or lattice vibrations.

2. How is the mean free time/path related to the electrical conductivity of a material?

The mean free time/path is inversely related to the electrical conductivity of a material. This means that materials with a longer mean free time/path have higher conductivity because their particles can travel longer distances without being scattered, allowing for more efficient flow of charge.

3. What factors affect the mean free time/path in a solid state material?

The mean free time/path is affected by factors such as temperature, impurity concentration, and the type of lattice structure of the material. Higher temperatures and increased impurity concentration can lead to shorter mean free times/paths, while certain lattice structures (such as those with higher symmetry) can result in longer mean free times/paths.

4. How is the mean free time/path related to the lattice spacing of a material?

The mean free time/path is directly related to the lattice spacing of a material. Materials with larger lattice spacing have longer mean free times/paths because their particles have more space to travel without encountering obstacles. On the other hand, materials with smaller lattice spacing have shorter mean free times/paths due to a higher likelihood of particle collisions.

5. How can the mean free time/path be experimentally measured?

The mean free time/path can be experimentally measured using techniques such as transport measurement, where the electrical conductivity of a material is measured at different temperatures to determine the mean free time/path. Scattering experiments and simulations can also be used to directly measure the mean free time/path in a material.

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