[Pw_forum] This is a supercell, fractional translation are disabled ?

[Eyvaz Isaev]

Dear Kumar,

The message is just warning for you, a signal, be sure that your structure is correct. 
This prevents adding  additional nonfractional translations. So, it is OK, if you really use a supercell.

And this is very likely as according to http://cst-www.nrl.navy.mil/lattice/struk/aO2.html alpha-O2 is a  base-centered monoclinic lattice with 2 atoms in the unit cell, but  you used simple monoclinic with 4 atoms, that is why you got such kind message.

Bests,
Eyvaz.

-------------------------------------------------------------------

Prof. Eyvaz Isaev, 

Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden 

Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, 

isaev at ifm.liu.se, eyvaz_isaev at yahoo.com

--- On Thu, 8/12/10, sonu kumar <1009ukumar at gmail.com> wrote:

From: sonu kumar <1009ukumar at gmail.com>
Subject: [Pw_forum] This is a supercell, fractional translation are disabled ?
To: pw_forum at pwscf.org
Date: Thursday, August 12, 2010, 4:35 PM

Dear All QE users,

While doing scf calculations on alpha O2 crystal, i got a massage :

Found symmetry operation: I + (  0.0000 -0.5000 -0.5000)
     This is a supercell, fractional translation are disabled



Although code correctly predicts the space group, is there something wrong in 
the input coordinates?

However, i checked the structure in Xcrysden, and found it to be correct (i.e. correct bond 
lengths, angles, distances between atoms).



Can anybody help me out?

Below is the part of input file:

#################################################################
&system
    ibrav = 12,
    celldm(1)=9.5860, celldm(2)=1.06271, celldm(3)=0.67699, celldm(4)=-0.672625


    nat=4, ntyp=1,             
    nbnd=12,                   
    ecutwfc=40,                  
    ecutrho=300,              
 /

ATOMIC_SPECIES 
 O    8.0000 O.pbe-van_ak.UPF   

ATOMIC_POSITIONS (crystal)


O  0.171000  0.105000 0.000000 
O -0.171000 -0.105000 0.000000 
O  0.171000  0.605000 0.500000 
O -0.171000  0.395000 0.500000
#################################################################


With Kind Regards,


Sonu Kumar

Phd Student
Physics Department
Indian Institute of Technology 
Delhi-110016, India
web:-http://www.iitd.ac.in/


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