# Atomic positions of iron

abode harry
how do i determine the different atomic positions of iron (bcc) as the number of atom increases.

Mentor
What do you mean with "number of atom increases"? In solid iron, the atoms are always in a lattice. The lattice structure can depend on pressure and temperature (and the presence of other atoms), you can look it up in phase diagrams.

abode harry
thanks for the reply, but my question has not been answered .am trying to use quantum espresso to determine surface energy of iron.to do this, i need to increase the number of slab or layers. i need to know how to increase the atomic position, when increasing the layers.Please,i need someone to help me out

Mentor

So you are looking for coordinates of atoms in a bcc lattice? What is the orientation of the lattice in your coordinate system?
Do you know the lattice constant?

abode harry
the lattice constant for iron is 2.863 angstrom. orientation of the lattice, 100,010,001,111,110,101,011

Mentor
So you just have to add two layers (one for the "corners" one for the central atoms) each 2.863 angstrom?

To me, it is still unclear where exactly your problem is.

orientation of the lattice, 100,010,001,111,110,101,011
Which one?

abode harry
this is my input file. but my output is giving me error.overlap of 4 and 5

&control
calculation='scf'
restart_mode='from_scratch',
pseudo_dir = '/cygdrive/c/cygwin/espresso-4.2.1/pseudo/',
outdir='/home/ABODE HARRY/tmp/',
prefix='fe'
/
&system
ibrav = 3, celldm(1) =5.217, nat= 5, ntyp= 1,
ecutwfc = 40.0,ecutrho = 200.0,
report=1,
occupations='smearing', smearing='marzari-vanderbilt', degauss=0.05
noncolin = .true.
starting_magnetization(1) = 0.5
angle1(1) = 45.0
angle2(1) = 53.0
constrained_magnetization='total'
fixed_magnetization(1)=0.3,
fixed_magnetization(2)=0.4,
fixed_magnetization(3)=0.5,
lambda = 0.5
/
&electrons
conv_thr = 1.0e-9
mixing_beta = 0.3
/
ATOMIC_SPECIES
Fe 55.847 Fe.pz-nd-rrkjus.UPF
ATOMIC_POSITIONS
Fe 0.00 0.00 0.00
Fe 0.50 0.00 0.00
Fe 0.00 0.50 0.00
Fe 0.50 0.50 0.00
Fe 0.00 0.00 0.50
K_POINTS AUTOMATIC
4 4 4 1 1 1

abode harry
atomic position

this is my input file. but my output is giving me error.overlap of 4 and 5.i don't know if my coordinates are wrong.pls, could you help on how to determine the correct atomic positions

&control
calculation='scf'
restart_mode='from_scratch',
pseudo_dir = '/cygdrive/c/cygwin/espresso-4.2.1/pseudo/',
outdir='/home/ABODE HARRY/tmp/',
prefix='fe'
/
&system
ibrav = 3, celldm(1) =5.217, nat= 5, ntyp= 1,
ecutwfc = 40.0,ecutrho = 200.0,
report=1,
occupations='smearing', smearing='marzari-vanderbilt', degauss=0.05
noncolin = .true.
starting_magnetization(1) = 0.5
angle1(1) = 45.0
angle2(1) = 53.0
constrained_magnetization='total'
fixed_magnetization(1)=0.3,
fixed_magnetization(2)=0.4,
fixed_magnetization(3)=0.5,
lambda = 0.5
/
&electrons
conv_thr = 1.0e-9
mixing_beta = 0.3
/
ATOMIC_SPECIES
Fe 55.847 Fe.pz-nd-rrkjus.UPF
ATOMIC_POSITIONS
Fe 0.00 0.00 0.00
Fe 0.50 0.00 0.00
Fe 0.00 0.50 0.00
Fe 0.50 0.50 0.00
Fe 0.00 0.00 0.50
K_POINTS AUTOMATIC
4 4 4 1 1 1

Mentor
I have no idea how that config file works, so I don't see how I could help there.