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Hi,
I'm attempting to calculate substitutional energies of species in bulk, which require me to perform calculations of the substituted atoms in isolation.

I know that the energy without entropy of an atoms should be equal to zero within VASP's output. Some single atom species have converged (such as oxygen) and are significantly non-zero...order of .5eV. Others, the transition metals, are not converging at all.

I have tried to use, for consistency, the same input parameters as my bulk calculations, so spins are unpolarized. POTCARS are from the standard GGA pseudopotential (PW91 I think). To try and help SCF convergence, I have increased/decreased ENMAX, decreased AMIX and BMIX, increased/decreased KPOINTS and varied ISMEAR. No luck.

The dE in OSZICAR just flip flop between negative and positive no matter how much I increase NELM.

Some of the transition metals converge if spin polarization is added in. For those, could I just subtract off the correction found in the vasp documentation?

Any suggestions?

Thank you

please note that for some transition metal atoms the POTCAR is generated for the ground state of the atom in its bulk phase (ground state) , which may not be in accordance with HUND's rule for the free atom (please have a look at the online manual).
--> you HAVE to add spin polarizarion, unless the configuration is s2d10
-- you may also have to add the magnetic moment of the free atom explicitely (NUPDOWN, or FERWE and FERDO) to converge to the correct configuration and degeneracies
-- use ISMEAR = 0 and decrease SIGMA to about 0.001

-- please don't forget that you have to use the Gamma point only for free atoms