energy & force tolerance

Message

kusiu · #1 Post by **kusiu** » Fri Jan 25, 2008 1:30 pm

Hi
I've read in the VASP's manual that an option EDIFFG is responsible for the ions relaxation tolerance. It has a meaning of energy tolerance If it's positive and force tolerance in the case of negative values.

Is it somehow possible to set both tolerances?

Krzysztof

#2 Post by **admin** » Mon Jan 28, 2008 9:02 am

the values to choose depend on the problem you want to solve:
--) EDIFFG 0
this depends of the required accuracy of the total energy you need for your investigation, which may vary over several ranges of magnitude: the possible error in energy due to relaxation convergence should be at least one order of magnitude smaller than the requested accuracy of the effect you are investigating: eg, if you need to determine some adsorption energy to an accuracy of meV, EDIFFG should be 1e-4 or 1e-5 at least. (and, correspondingly EDIFF 1e-05 or 1e-06)

kusiu · #3 Post by **kusiu** » Fri Apr 25, 2008 12:32 pm

Thank you for response but it is not what I meant. I mean about setting both tolerances in the same time. For example calculation are stopped when energy difference is less than 1e-05 eV >>AND<< maximal force is less than 0.01 eV/A.

Thank you in advance:
Krzysztof

#4 Post by **admin** » Tue Apr 29, 2008 7:13 am

this is not possible. Only the first entry for each tag in INCAR is taken for input from INCAR, multiple settings are ignored