cutoff might be too small for a reliable computation of the stress.
other than that I see no big issue in your input
stefano
On 25/12/18 04:35, Gui Wei wrote:
Hi,
When optimizing the lattice constant of bcc Fe,the result is a=2.830A，
which is in disagreement with experimentally derived structural
parameter a=2.863A.Could someone give me some advice?
&CONTROL
calculation = 'vc-relax'
prefix='Fe1',
pseudo_dir = '/public/home/duan1/gw2/pseudo/',
outdir='/public/home/duan1/gw2/tempdir/'
tprnfor = .true.
tstress = .true.
/
&SYSTEM
ibrav= 1,
A=2.8664
nat= 2
ntyp= 1
occupations='smearing',
smearing='mp',
degauss=0.02,
ecutwfc =37
ecutrho =240
nspin = 2
starting_magnetization(1) = 0.4
/
&ELECTRONS
conv_thr = 1.0d-8
mixing_beta = 0.7
/
&IONS
ion_dynamics = 'bfgs'
/
&CELL
cell_dynamics = 'bfgs'
/
ATOMIC_SPECIES
Fe 55.847 Fe.pbe-n-kjpaw_psl.0.2.4.UPF
ATOMIC_POSITIONS crystal
Fe 0.0000000000000000 0.0000000000000000 0.0000000000000000
Fe 0.5000000000000001 0.5000000000000001 0.5000000000000001
K_POINTS automatic
8 8 8 0 0 0
The result:
CELL_PARAMETERS (alat= 5.41671099)
0.987418499 0.000000000 0.000000000
0.000000000 0.987418499 0.000000000
0.000000000 0.000000000 0.987418499
Gui Wei
School of Mechanical Engineering，Chongqing University, China
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