[Pw_forum] Mg.pz-n-vbc.UPF O.pz-mt.UPF give negative pressure in MgO md calculation

[Lawrence Lee]

Dear all,

The pressure calculated by using the pseudo-potential (Mg.pz-n-vbc.UPF) and (O.pz-mt.UPF) is negative! These two pp were downloaded from www.pwscf.org.

I've tried exactly the same configuration but using (Mg.pw91-np-van.UPF) and (O.pw91-van_ak.UPF) (also downloaded from www.pwscf.org), the results are fine.

Here, I attach my simple input file. Please help see whether I am making mistakes or the pp have some problem.

Thanks in advance for any comments.

Lawrence


 &control
    calculation='md',
    restart_mode='from_scratch',
    nstep=3000,
    dt=20,
    tstress=.TRUE.
    tprnfor=.TRUE.
    pseudo_dir='~/espresso-3.1.1/pseudo',
    outdir='./tmp/',
 /
 &system
    ibrav=1, celldm(1)=7.80,
    nat=8 , ntyp=2,
    ecutwfc=30,
    ecutrho=240,
    nosym=.true.
 /
 &electrons
    conv_thr=1.d-8,
    mixing_mode='plain',
    mixing_beta=0.7d0,
    diagonalization='david',
 /
 &ions
    ion_dynamics='verlet',
    pot_extrapolation='second-order',
    wfc_extrapolation='second-order',
    ion_temperature='rescaling',
    tempw=300,
    delta_t=1,
    nraise=1
 /
ATOMIC_SPECIES
 Mg  24.305   Mg.pz-n-vbc.UPF
  O  16.000   O.pz-mt.UPF
ATOMIC_POSITIONS {alat}
 Mg   0.00   0.00   0.00
 Mg   0.50   0.50   0.00
 Mg   0.50   0.00   0.50
 Mg   0.00   0.50   0.50
  O   0.50   0.00   0.00
  O   1.00   0.50   0.00
  O   1.00   0.00   0.50
  O   0.50   0.50   0.50
K_POINTS {automatic}
   2 2 2 0 0 0

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