ABINIT Discussion Forums

Hi,
I want to optimize the supercell organization and only relax the surface atoms. But it has a error, and this is my .in file :
occopt 4
tsmear 0.04
acell 4.0345 4.0345 18.0345 Angstrom
angdeg 90.0000 90.0000 90.0000
ntypat 3
znucl 56 22 8
natom 7
typat 1 1 2 3 3 3 3
xcart 0 0 0
0 0 0.2237
0.5 0.5 0.11185
0.5 0 0.11185
0 0.5 0.11185
0.5 0.5 0
0.5 0.5 0.2237
chksymbreak 0
natfix 5
iatfix 1 3 4 5 6
ecut 13
ixc 14
pawecutdg 50
optcell 0
ionmov 3
ntime 500
tolmxf 6.0d-4
nstep 100
tolvrs 1.0d-20
iscf 17
npulayit 20
ngkpt 6 6 1
nshiftk 2
shiftk 0.5 0.0 0.0
0.0 0.5 0.0
the error is :
fixsym: ERROR -
Atom number 2 is symmetrically equivalent to atom number 1,
but according to iatfix, iatfixx, iatfixy and iatfixz, they
are not fixed along the same directions, which is forbidden.
Action : modify either the symmetry or iatfix(x,y,z) and resubmit.

I donot think the atom 1 and 2 are in the same place, because the c of the cell is 18.03 A, the atom 2 is not in the cell boundary. Can you tell why ?

When I remove these two lines :
natfix 5
iatfix 1 3 4 5 6
and I restart the file ,it also has an error:
chkpawovlp : ERROR -
PAW SPHERES ARE OVERLAPPING !
Distance between atoms 1 and 3 is : 0.71590
PAW radius of the sphere around atom 1 is: 2.52098
PAW radius of the sphere around atom 3 is: 1.82908
This leads to a (voluminal) overlap ratio of 99.95 %

I use the paw pseudopotentials which are transformed by the ultrasoft pseudopotentials , used the sofeware of USpp2Abinit.
This is my first time to use the paw pseudopotentials , and I donot konw what I should notice. Can someone tell me where is wrong?
Thanks~

you probably want xred instead of xcart.

I agree the 2 atoms should not be equivalent, and you should be able to leave the constraint lines in the input.