Tutorial VASP. Difference in energy

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autieri · #1 Post by **autieri** » Wed Apr 06, 2011 2:34 pm

Dear All,

I am new on VASP and I tried to do the tutorial on the web site.
For atoms and molucule I have no problem. The energy, that I found, are exactly equal to the energy in the pdf of the handson
When I did the calculation with a k-mesh for solids I had some little discrepancies between the energy of my calculation and the energy of the pdf file of the handson. In particular, I found a difference that is about 0.1% for the energy like function of the volume in Silicon fcc and Silicon diamond (Tutorial 2.1 and 2.4).
It is normal? Can be a problem?

Thanks
Carmine

alex · #2 Post by **alex** » Wed Apr 06, 2011 3:11 pm

Most likely the convergence criteria isn't tight enough for that kind of comparison.

Cheers,

Alex

#3 Post by **admin** » Wed Apr 06, 2011 4:03 pm

please note that the vasp-workshop excecises were run with a very old version of vasp.4.6, you may probably
1) use a different vasp version
2) use more than one CPU
3) the convergence criteria are not tight, as alex indicated, this may be a reason as well

autieri · #4 Post by **autieri** » Fri May 13, 2011 12:49 pm

OK. thanks