Solution LAB1 diamond lattice parameter

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Lattice parameter of diamond

Given the convergence study of the total energy as a function of the k-point grid (as done in previous exercises), here we set the k-grid to a converged value, say

 nk=8

and perform a series of total energy calculations at different lattice parameters, for several values of the kinetic energy cutoff.

For each cutoff, Etot vs alat is fit (eg using a python script provided) and the minimum is extracted.

The scripts developed in previous exercises can be used to run multiple calculations and to extract the data.

Results as a function of the cutoff

In the following you can find the fitted lattice parameter as a function of the kinetic energy cutoff used in the calculations.

 # Ecut     alat
   20      6.8354274
   30      6.686406
   40      6.727857
   50      6.6744762
   60      6.6694212
   80      6.664164
  100      6.6647706
  120      6.6639618
  140      6.6639618
  160      6.6639618