[Pw_forum] scan the lattice constant

[XunLei Ding]

Dear all,
I do a calculation to get the lattice constant of Ni crystal.
I scan the lattice constant from 6.60 to 6.70 a.u. using the bash file below.
The experimental value is 6.66 and is consistent with my result.
But it is clear that the curve departs into two parts at 6.66. 
(see the picture at http://www.bsc.ustc.edu.cn/~dxl/download/Graph1.JPG)
Would you tell my why and how to solve this problem.

Thank you!

Ding Xunlei

for a0 in  6.60 6.61 6.62 6.63 6.64 6.65 6.66 6.67 6.68 6.69 6.70
do
cat >test.in<<!
&control
    calculation='scf'
    restart_mode='from_scratch',
    pseudo_dir = '/home/bsc/dxl/pseudo/',
    outdir='./'
    prefix='zz'
    tprnfor = .true.,
for a0 in  6.64
do
cat >test.in<<!
&control
    calculation='scf'
for a0 in  6.65
do
cat >test.in<<!
&control
    calculation='scf'
    restart_mode='from_scratch',
    pseudo_dir = '/home/bsc/dxl/pseudo/',
    outdir='./'
    prefix='zz'
    tprnfor = .true.,
    tstress = .true.
 /
 &system
    ibrav=2, celldm(1) =$a0
    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
    electron_maxstep= 200
    diagonalization=''
    conv_thr = 1.0e-8
    mixing_beta = 0.2
 &cell
    cell_dynamics = 'none'
    cell_factor = 1.2
 /
 &ions
     ion_dynamics = 'damp'

 /
ATOMIC_SPECIES
 Ni 58.69 Ni.pbe-nd-rrkjus.UPF
ATOMIC_POSITIONS
 Ni       0.00000000   0.000000000   0.000000000  1 1 1
K_POINTS (automatic)
13 13 13 1 1 1
!