[Pw_forum] choice of the pseudo, Ni(110)

[Varki Pagan (Peressi)]

Hi all,

i'm using pw in order to study a Ni(110) surface.

I' m now just fixing the bulk properties, so i ran some loops to study the 
variation of the minimum value of the energy and of the alat in the bulk.

after doing that stuff, i tried using a different pseudo, obtaining quite 
different results.

i' m sorry for probably it' s a silly question, but how do i choose my 
pseudo ?

first used pseudo :

          Perdew-Zunger (LDA) exch-corr
 	 nonlinear core-correction
 	 semicore state d in valence
 	 Rabe Rappe Kaxiras Joannopoulos (ultrasoft)

obtaining a0 = 6.47 alat and Emin =  -85.72192 Ry


second used pseudo :

          Perdew-Burke-Ernzerhof (PBE) exch-corr
 	 nonlinear core-correction
 	 semicore state d in valence
 	 Rabe Rappe Kaxiras Joannopoulos (ultrasoft)

obtaining a0 = 6.66 alat and Emin = -85.89509 Ry


others parameters fixed in both the runs ( obtained as best choice for a 
desired accuracy after different evaluation runs) :

  &control
     calculation='scf'
     restart_mode='from_scratch',
     pseudo_dir = '/home/espresso/pseudo/',
     outdir='/tmp/'
     prefix='ni'
     tprnfor = .true.,
     tstress = .true.
  /
  &system
     ibrav=2, celldm(1) =6.80, nat=1, ntyp=1,
     nspin = 2,  starting_magnetization(1)=0.7,
     ecutwfc = 24.0, ecutrho = 288.0,
     occupations='smearing', smearing='methfessel-paxton', degauss=0.01
  /
  &electrons
     diagonalization=''
     conv_thr = 1.0e-8
     mixing_beta = 0.7
  /
ATOMIC_SPECIES
  Ni 58.69 NiUS.RRKJ3.UPF

ATOMIC_POSITIONS
  Ni 0.0 0.0 0.0
K_POINTS (automatic)
  5 5 5 1 1 1



So, i apologize once more 'cause probably it's a silly question, and thank 
you all in advance for your attention.

bye,

varki pagan.