[Pw_forum] Problem with lattice optimization

[sayan chaudhuri]

Dear All,

 I am trying to optimize the lattice parameter of Fe2TiSb by running the
following code self consistently. But somehow it is giving a lattice
parameter of 6.82 Angstrom, which is nowhere near to the lattice parameter
I am getting experimentally ( 6.017 Angstrom).
My input file is the following,














































* &CONTROL                 calculation = 'scf' ,
restart_mode = 'from_scratch' ,                  wf_collect = .true.
,                      pseudo_dir = './',
outdir='./'                      prefix = 'fta' ,
verbosity = 'low' ,                     tstress = .false.
,                     tprnfor = .false. , / &SYSTEM
ibrav = 2,                   celldm(1) =12.92,                         nat
= 4,                        ntyp = 3,                     ecutwfc = 60.0
,                     ecutrho = 250.0 ,                        nbnd =
30,                 occupations = 'smearing' ,                     degauss
= 0.002 ,                    smearing = 'marzari-vanderbilt'
,                       nspin = 2 ,   starting_magnetization(1) = 0.5,
starting_magnetization(2) = 0.6,   starting_magnetization(3) =
0.5, / &ELECTRONS            electron_maxstep = 200,
conv_thr = 1e-8 ,                 mixing_mode = 'plain' ,
mixing_beta = 0.3 ,             diagonalization = 'david'
, /ATOMIC_SPECIES   Fe   55.84500  Fe.pbe-mt_fhi.UPF    Ti   47.86700
Ti.pbe-mt_fhi.UPF    Sb  121.76000  Sb.pbe-mt_fhi.UPF ATOMIC_POSITIONS
Fe      0.250000000    0.250000000    0.250000000       Fe
0.750000000    0.750000000    0.750000000       Sb      0.000000000
0.000000000    0.000000000       Ti      0.500000000    0.500000000
0.500000000    K_POINTS {automatic}   2 2 2   0 0 0 *

Where I am changing the celldm(1) in each run.

Please tell me what am I doing wrong in the calculation.

 Thanking you in advance,

               Sayan Chaudhuri
               IIT Indore
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