atomic energy
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D.H.Tang
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- Joined: Thu Oct 15, 2009 2:43 pm
atomic energy
I used PAW pseudopotential to calculate a single atomic energy, but the calculated value was postive.I don't know why?Please help me , what to solve this problem?
Last edited by D.H.Tang on Sat Oct 17, 2009 8:40 am, edited 1 time in total.
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forsdan
- Sr. Member
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atomic energy
If you get a positive value this means that you have reached a configuration that has higher energy than the reference state. Please check
1. if the calculation converges before the maximum number of electronic (NELM) steps have been taken. This is by default set to 60. If it doesn't converge before that please either increase NELM or try the approaches suggested in the pdf-talks:
http://cms.mpi.univie.ac.at/vasp-worksh ... ectron.pdf
page 21 and forward.
2. which magnetic state the calculation converged to. Depending on your MAGMOM settings you sometimes get convergence to a magnetic state that is higher in energy than the ground state energy. If this happens please try with a different initial guess for MAGMOM. The experimental value multiplied with 1.2 or 1.5 is typically a good starting point.
The general procedure to calculate the groundstate of atoms can be found in the manual:
http://cms.mpi.univie.ac.at/vasp/vasp/node230.html
http://cms.mpi.univie.ac.at/vasp/vasp/node231.html
Hope this helps,
Cheers,
/Dan
<span class='smallblacktext'>[ Edited Sun Oct 18 2009, 11:22AM ]</span>
1. if the calculation converges before the maximum number of electronic (NELM) steps have been taken. This is by default set to 60. If it doesn't converge before that please either increase NELM or try the approaches suggested in the pdf-talks:
http://cms.mpi.univie.ac.at/vasp-worksh ... ectron.pdf
page 21 and forward.
2. which magnetic state the calculation converged to. Depending on your MAGMOM settings you sometimes get convergence to a magnetic state that is higher in energy than the ground state energy. If this happens please try with a different initial guess for MAGMOM. The experimental value multiplied with 1.2 or 1.5 is typically a good starting point.
The general procedure to calculate the groundstate of atoms can be found in the manual:
http://cms.mpi.univie.ac.at/vasp/vasp/node230.html
http://cms.mpi.univie.ac.at/vasp/vasp/node231.html
Hope this helps,
Cheers,
/Dan
<span class='smallblacktext'>[ Edited Sun Oct 18 2009, 11:22AM ]</span>
Last edited by forsdan on Sun Oct 18, 2009 8:16 am, edited 1 time in total.