[Pw_forum] Problem with PAW vs. USP

[Lorenzo Paulatto]

It is possivble that one_atom_occupation does not work with PAW, I've never 
tried it. Or maybe it is failing because the orbitals are not in the order you 
expect. I hope to be able to have a look at it in the future, although it 
won't be very soon

thank you for sharing your problem!

On Wednesday, October 14, 2015 08:39:03 AM Vic Bermudez wrote:
> Hello Lorenzo,
> 
> 	Thank you for your comments. Yes, getting the free-atom energy right is
> tricky. Below is a sample input file that, when used with a USPP and not a
> PAW PP, gives the correct Zr free-atom energy. I say "correct" because the
> correct cohesive energy (i.e., very close to experiment) is then obtained
> for the bulk metal. The starting magnetization value comes from the fact
> that 12 electrons (2 of which are unpaired in the (3)F ground state) are
> treated explicitly, whence starting_magnetization(1) = 2/12 = 0.16667.
> 	This same input file does not work correctly in a PAW calculation, probably
> because of the use of the OCCUPATIONS card. For PAW I was able to get the
> correct free-atom energy by removing:
> 
> 	occupations='from_input',
> 	one_atom_occupations=.TRUE.,
> 	starting_magnetization(1)=0.16667
> 
> and
> 
> 	OCCUPATIONS
> 	1 1 1 1 1 1 0 0 0 1 0 0 0
> 	1 1 1 1 0 0 0 0 0 1 0 0 0
> 
> and simply using tot_magnetization=2.0. The resulting free-atom energy is
> then very close to that given in Giovanni Cantele's message from earlier
> today, and the correct cohesive energy is then obtained.
> 	Hopefully other users will find this helpful.
> 
> Best Wishes,
> Vic Bermudez
> 
> Victor M. Bermudez
> E-mail: bermudez at alum.mit.edu
> 
> 
> ________________ Sample Free-Atom Input File ____________
> 
> 
> &CONTROL
> calculation='scf',
> title='free Zr atom - should give (3)F ground state - using PBE/PAW',
> pseudo_dir='/lustre/cmf/scratch/b/bermudez/QE_PP/',
> verbosity='high',
> wf_collect=.TRUE.
> /
> 
> &SYSTEM
> ibrav=1,
> a=40.0,
> nat=1,
> ntyp=1,
> nbnd=13,
> ecutwfc=40.0,
> ecutrho=320.0,
> nosym=.TRUE.,
> nspin=2,
> occupations='from_input',
> one_atom_occupations=.TRUE.,
> starting_magnetization(1)=0.16667
> /
> 
> &ELECTRONS
> electron_maxstep=200,
> conv_thr=1.0D-7,
> mixing_beta=0.7D0,
> mixing_ndim=8,
> mixing_mode='plain',
> startingwfc='random'
> /
> 
> ATOMIC_SPECIES
> Zr 91.22   Zr.pbe-spn-kjpaw_psl.0.2.3.UPF {** NOTE ** paw should not be used
> here !}
> 
> ATOMIC_POSITIONS angstrom
> Zr   0.000 0.000 0.000
> 
> K_POINTS automatic
> 1 1 1 0 0 0
> 
> OCCUPATIONS
> 1 1 1 1 1 1 0 0 0 1 0 0 0
> 1 1 1 1 0 0 0 0 0 1 0 0 0
> 
> 
> 
> 
> 
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum

-- 
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
+33 (0)1 44 275 084 / skype: paulatz
http://www.impmc.upmc.fr/~paulatto/
23-24/4é16 Boîte courrier 115, 
4 place Jussieu 75252 Paris Cédex 05