The ABINIT Users Mailing List ( CLOSED )

[Nuno Galamba <ngalamba@cii.fc.ul.pt>]

Dear Abinit users

I have a simple question regarding the choice of ecut for an arbitrary system.

 By doing a calculation for different values of ecut (say, 
10,15,20,25,30,35,40,45,50 Hartrees) for a given value of toldff (say 10-4 
Ha/Bohr) one can  observe a plateau at which energy converges to. 

Now the question is, say the energy is converged for ecut=30 Ha (meaning it 
does not change up to the first 5 digits), in principle the Hellmann-Feynman 
forces on every particle of the system should be converged too.

I am not quite sure this is the case. I observe that the force on the 
particles of the system are not the same. These are of the order of 10-6 
Ha/Bohr. Souldn't one expect some kind of convergence behavior for the force 
on every particle when increasing systematically the number of plane waves 
for a given calculation?

Thanks in advance


-- 
N. Galamba