[Pw_forum] VC-RELAX and Convergence Test

[Mofrad, Amir Mehdi (MU-Student)]

Dear all,


Let's say we want to optimize a configuration (and find the equilibrium lattice constant) but we don't know the optimal value of ecut (ecutrho) and/or k-points. My question is which one of the following procedure should be followed in order to find the converged values and is more accurate?


1. Do the vc-relax calculation for different values of ecut. Find the one that gives the converged value of total energy and the corresponding value of CELL_PARAMETER is the final lattice constant.



         or


2. Do scf calculation for different values of cutoff, choose the converged value and then do the vc-relax with that converged value of ecut and find the lattice constant.


Any help would be thoroughly appreciated.


Best,


Amir M. Mofrad

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