energy & force tolerance

Problems running VASP: crashes, internal errors, "wrong" results.


Moderators: Global Moderator, Moderator

Post Reply
Message
Author
kusiu
Newbie
Newbie
Posts: 2
Joined: Mon May 29, 2006 1:11 pm
License Nr.: 165

energy & force tolerance

#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
Last edited by kusiu on Fri Jan 25, 2008 1:30 pm, edited 1 time in total.

admin
Administrator
Administrator
Posts: 2921
Joined: Tue Aug 03, 2004 8:18 am
License Nr.: 458

energy & force tolerance

#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)
Last edited by admin on Mon Jan 28, 2008 9:02 am, edited 1 time in total.

kusiu
Newbie
Newbie
Posts: 2
Joined: Mon May 29, 2006 1:11 pm
License Nr.: 165

energy & force tolerance

#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
Last edited by kusiu on Fri Apr 25, 2008 12:32 pm, edited 1 time in total.

admin
Administrator
Administrator
Posts: 2921
Joined: Tue Aug 03, 2004 8:18 am
License Nr.: 458

energy & force tolerance

#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
Last edited by admin on Tue Apr 29, 2008 7:13 am, edited 1 time in total.

Post Reply