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I am doing some calculation on GaN, i need 8 or 16 atoms xred. this is my input file
ndtset 4
#Definition of the k-point grids
kptopt 1 # Option for the automatic generation of k points, taking
# into account the symmetry
nshiftk 4
shiftk 0.5 0.5 0.5 # These shifts will be the same for all grids
0.5 0.0 0.0
0.0 0.5 0.0
0.0 0.0 0.5

ngkpt 6 6 6 # Definition of the different grids
getwfk -1 # This is to speed up the calculation, by restarting
# from previous wavefunctions, transferred from the old


#Definition of the planewave basis set
ecut 55 # Maximal kinetic energy cut-off, in Hartree

#Definition of the SCF procedure
nstep 100
toldfe 1.0d-7
diemac 12.0
iscf 7


#optimization parameters
optcell 1
ionmov 3
#ntime 10
dilatmx 1.05
ecutsm 0.5
strfact 100
tolmxf 5.0d-5

# definition of unit cell
acell: 3*9.3
acell+ 3*0.1
chksymbreak 0
chkprim 0
rprim 0 0.5 0.5
0.5 0 0.5
0.5 0.5 0

#alchemical input
znucl 49 7
nband 36
ntypat 2
natom 8
npsp 2
typat 1 1 1 1 2 2 2 2
#ntypalch 1
#mixalch 0.25 0.75


xred 0.0 0.0 0.0
0.5 0.5 0.5
0.1 0.1 0.5
0.5 0.5 1.0
0.25 0.25 0.25
0.25 0.25 0.75
0.25 0.75 0.75
0.75 0.75 0.75

occopt 1
ixc 11
But in the log file structure im having is triclinic and not FCC. this is part of my log file
symlatt : the Bravais lattice is cF (face-centered cubic)
xred is defined in input file
ingeo : takes atomic coordinates from input array xred

symlatt : the Bravais lattice is cF (face-centered cubic)

symlatt : the Bravais lattice is cF (face-centered cubic)

--- !COMMENT
message: |
The Bravais lattice determined only from the primitive
vectors, bravais(1)= 7, is more symmetric
than the real one, iholohedry= 1, obtained by taking into
account the atomic positions. Start deforming the primitive vector set.
src_file: symbrav.F90
src_line: 201
...


symlatt : the Bravais lattice is hR (rhombohedral)

--- !COMMENT
message: |
The Bravais lattice determined from modified primitive
vectors, bravais(1)= 5, has a lower symmetry than before,
but is still more symmetric than the real one, iholohedry= 1
obtained by taking into account the atomic positions.
src_file: symbrav.F90
src_line: 210
...


symlatt : the Bravais lattice is mC (one-face-centered monoclinic)
DATASET 3 : space group P1 (# 1); Bravais aP (primitive triclinic)

getdim_nloc : deduce lmnmax = 16, lnmax = 4,
lmnmaxso= 16, lnmaxso= 4.
memory : analysis of memory needs
================================================================================
Values of the parameters that define the memory need for DATASET 3.
intxc = 0 ionmov = 3 iscf = 7 xclevel = 2
lmnmax = 4 lnmax = 4 mband = 36 mffmem = 1
P mgfft = 48 mkmem = 432 mpssoang= 4 mpw = 4849
mqgrid = 3001 natom = 8 nfft = 110592 nkpt = 432
nloalg = 4 nspden = 1 nspinor = 1 nsppol = 1
nsym = 1 n1xccc = 2501 ntypat = 2 occopt = 1
================================================================================
P This job should need less than 1210.181 Mbytes of memory.
Rough estimation (10% accuracy) of disk space for files :
_ WF disk file : 1150.692 Mbytes ; DEN or POT disk file : 0.846 Mbytes.
================================================================================

Biggest array : cg(disk), with 1150.6924 MBytes.
memana : allocated an array of 1150.692 Mbytes, for testing purposes.
memana : allocated 1210.181 Mbytes, for testing purposes.
The job will continue.
Now i need xred for 8 or 16 atom that will be fcc with space group number 216.
Thanks