[Pw_forum] Problem with ibrav=0 in supercell calculations

[DHRUV SINGH]

Hi everyone,

I am trying to do a supercell calculation of InAs (zinc blende structure) using the following input file(ibrav=0 and specifying cell parameters with cubic symmetry)

 &control
    calculation='scf'
    restart_mode='from_scratch',
    tstress = .true.
    tprnfor = .true.
    prefix='inas',
    pseudo_dir = '/home/ba01/u110/singh36/espresso-4.1.3/pseudo/',
    outdir='./tmp'
 /
 &system
    ibrav=0,
    celldm(1)=11.05,
    nat=  8,
    ntyp= 2,
    ecutwfc =25.0
    ecutrho=250.0
 /
 &electrons
    conv_thr =  1.0d-8
    mixing_beta = 0.7
 /
ATOMIC_SPECIES
 In  114.818  In.pz-bhs.UPF
 As  74.921  As.pz-bhs.UPF
CELL PARAMETERS{cubic}
 1.0 0.0 0.0
 0.0 1.0 0.0
 0.0 0.0 1.0

ATOMIC_POSITIONS {crystal}
 In 0.00 0.00 0.00
 As 0.25 0.25 0.25
 In 0.50 0.50 0.00
 As 0.75 0.75 0.25
 In 0.00 0.50 0.50
 As 0.25 0.75 0.75
 In 0.50 0.00 0.50
 As 0.75 0.25 0.75
K_POINTS {automatic}
 4 4 4 0 0 0

Strangely enough an scf run does not read the cell parameters card and I get an error

 Waiting for input...
Warning: card CELL PARAMETERS{CUBIC} ignored
Warning: card  1.0 0.0 0.0 ignored
Warning: card  0.0 1.0 0.0 ignored
Warning: card  0.0 0.0 1.0 ignored

 %%%%%%%%%%%%%%%%%%%%%%%%%
     from read_cards : error #         1
     ibrav=0: must read cell parameters
 %%%%%%%%%%%%%%%%%%%%%%%%%

     stopping ...

--------

I have run a few calculations in the past with the cubic supercell specifying different values of cell parameters and they work fine. Also the calculation runs fine with ibrav=1 (and not specifying the cell parameters). However, I am not able to pin down the mistake I am making here (Are we not allowed to specify a free lattice if it has equal cell parameters?).

Thanks,
Dhruv Singh
School of Mechanical Engineering, Purdue University
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