I am studying Si nanowires with different cross sections. In my work, I plan to evaluate the thermoelectric performance variation between different configurations. To achieve this, my current approach is to evaluate the thermal conductivity of the nanowires using classical molecular dynamics simulations whereas the electrical properties are extracted through DFT calculations using SIESTA coupled with BoltzTraP2 (to solve the Boltzmann transport equation under the relaxation time approximation).

The drawback of this methodology is that BoltzTraP2 gives the the electrical conductivity of the structure per unit relaxation time. However, since I am interested in determining the relative variation of these properties between individual structures, I can still compare the Seebeck coefficient and electrical conductivity/ relaxation time and determine which structure is more suited for thermoelectric applications.

However, this whole comparison depends on whether the electron relaxation time remains constant between the individual configurations or not. Given that I use the same material (Si) and nanowires of similar diameters, would this assumption be reasonable?

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    $\begingroup$ I gave my +1 long ago, but just came back to check-in and see how you're doing with this. Since almost 3 months have passed since you asked this, do you have any update that you should share with us? $\endgroup$ Jan 27, 2022 at 0:33
  • $\begingroup$ @NikeDattani, the answer is that this comparison cannot be drawn without the electron relaxation time, since it should vary significantly between individual structures. However, I am still in the process of evaluating the relaxation time using the Deformation Potential method as answered in a previous question. So I think that it would be best to wait till the results are actually known. $\endgroup$
    – PBH
    Jan 27, 2022 at 1:50

1 Answer 1


I have been working on evaluating the electron relaxation time in these structures for some time now. From what I found out using Deformation Potential theory calculations, the assumption I made earlier was incorrect. I calculated the average electron relaxation time in all the structures, and there were sufficiently significant differences between them.

Although I have seen some published articles using a constant 1fs electron relaxation time just to eliminate the per relaxation time component of the electronic transport properties, I saw that the relaxation time in my cases varied between 2.5fs (Structure A) and 6.7fs (Structure B). If I had used the same 1fs relaxation time for both structures, the thermo-electric performance of structure A would have been better. However in reality, it had worse performance than Structure B. Because of this, it would probably be the best to actually evaluate the electron relaxation time if possible.


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