[Pw_forum] improper symmetry analysis

[Kun Yin]

Dear Users and Developers:

I met a weird phenomenon when calculating with a fcc crystal (sg. Fd-3m). I
used the same crystal structure. The only difference among the input files
is the value of parameter celldm(1). The crystal symmetries recognized by
pw.x  are not consistent. There are also some warnings like "symmetry
operation # not allowed" in the head of the output files.

Below is part of my shell script including input file:

primitive_volumes="1056.5261 1009.8683 972.0540 940.4584 913.4519 889.9579
869.2306 850.7331 834.0674"
i=0;
for v in $primitive_volumes; do
a=`echo 'scale=6; e(l('$v'*0.5)/3.0)' | bc -l`
i=`expr $i + 1`
cat > temp.in << EOF
 &control
    calculation = 'relax'
    restart_mode='from_scratch',
    prefix='temp',
    tprnfor = .true.
    pseudo_dir = '$PSEUDO_DIR'
    outdir = '$TMP_DIR'
 /
 &system
    ibrav = 0, celldm(1)=$a,
    nat = 14, ntyp = 3,
    ecutwfc = 45.0, ecutrho = 450.0
 /
 &electrons
    conv_thr =  1.0d-8
 /
 &ions
    ion_dynamics='bfgs'
 /
ATOMIC_SPECIES
 Mg  24.305  Mg.pw91-np-van.UPF
 Al  26.9815  Al.pw91-n-van.UPF
 O   15.9994   O.pw91-van_ak.UPF
K_POINTS automatic
6 6 6 0 0 0
CELL_PARAMETERS cubic
   1.0       1.0       0.0
   1.0      -1.0       0.0
   1.0       0.0       1.0
ATOMIC_POSITIONS crystal
Mg    0.12500000    0.87500000    0.25000000
Mg    0.87500000    0.12500000    0.75000000
Al    0.50000000    0.50000000    0.00000000
Al    0.50000000    0.00000000    0.50000000
Al    0.00000000    0.50000000    0.00000000
Al    0.50000000    0.50000000    0.50000000
O    0.26230000    0.73770000    0.52460000
O    0.73770000    0.26230000    0.47540000
O    0.73770000    0.71310000    0.02460000
O    0.26230000    0.28690000    0.97540000
O    0.71310000    0.73770000    0.52460000
O    0.28690000    0.26230000    0.47540000
O    0.73770000    0.26230000    0.02460000
O    0.26230000    0.73770000    0.97540000
EOF

Check symmetry operations in output files (grep 'Sym.Ops' *.out):
temp-1.out:     48 Sym.Ops. (with inversion)
temp-2.out:     48 Sym.Ops. (with inversion)
temp-3.out:     48 Sym.Ops. (with inversion)
temp-4.out:     12 Sym.Ops. (with inversion)
temp-5.out:     12 Sym.Ops. (with inversion)
temp-6.out:     12 Sym.Ops. (with inversion)
temp-7.out:     12 Sym.Ops. (with inversion)
temp-8.out:     48 Sym.Ops. (with inversion)
temp-9.out:     48 Sym.Ops. (with inversion)

I think the correct symmetry operations number should be 48 for this
crystal. I don't know how to fix this "improper symmetry analysis" problem.
Can you help me?

--
Kun Yin
Ph.D. Candidate
School of Earth Sciences and Engineering
Nanjing University
502 Geological Laboratory Building
22 Hankou Road
Nanjing 210093
P.R. China

email: kyin.cn at gmail.com