[Wien] Effective mass calculation

[Marcelo Barbosa]

Dear Sirs,

I’m having some trouble calculating the effective mass using the results from the band structure, so I’m going to explain the procedure that I tried.

First I compared the band structure with previous simulations and experimental results and it is correct.
Looking into the file case.spaghetti_ene, I can confirm that the k-points are in units of 2*pi/bohr (as explained in https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg05273.html <https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg05273.html>).
Therefore, in order to fit the curve to the parabolic function E = hbar^2 * k^2 / (2 * m) to get the value of m, I transformed the 4th column from Bohr to Angstrom by multiplying it by 1.8897259886, squared it and subtracted to the 5th column the energy value at k=0 to have E(k=0) = 0.
If I plot the resulting E vs k^2, I get a straight line for the first few points and so I calculate the slope in that range, which is around 9.9.
Then, using the relation m = hbar^2 / (2 * slope), using hbar in units of eV.s I calculate the effective mass.
The result I get is 0.024*me when I was expecting to get something around 0.28*me, so I’m wrong in one order of magnitude.
Could you please help me understand what I’m doing wrong?

Best regards,
Marcelo

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