The ABINIT Users Mailing List ( CLOSED )

["Josef W. Zwanziger" <jzwanzig@jzwanzig.org>]

Dear Doru, 

what always seems to work best in these face and base-centered structures is 
to set acell to 1.0 and carry the vector lengths in rprim. This is due to the 
way abinit will combine these variables internally. So in your case I would 
try

acell 3*1.0
rprim 2.695 5.552 0.000
     -2.695 5.552 0.000
      0.000 0.000 9.3274

let me know if this doesn't work--
Joe

 Josef W. Zwanziger
Professor of Chemistry
Canada Research Chair in NMR Studies of Materials
Director, Atlantic Region Magnetic Resonance Centre
Department of Chemistry
Dalhousie University
6274 Coburg Road
Halifax, Nova Scotia B3H 4J3 Canada
tel: +1.902.494.1960
fax: +1.902.494.1310
web: http://jwz.chem.dal.ca
jzwanzig@jzwanzig.org,jzwanzig@dal.ca



----- Original Message ----
> From: Doru Torumba <doru.torumba@cea.fr>
> To: forum@abinit.org
> Sent: Tuesday, December 9, 2008 9:20:27 AM
> Subject: [abinit-forum] alpha-U structure
> 
> Dear Abinit users,
> 
> I am trying to create the alpha-U structure, but for some reason I do not 
> get
> the correct space group (Cmcm, #63). In this structure there are 2 atoms per
> unit cell. Atomic positions are (y,-y,-1/4) and (-y,y,1/4) in units of 
> Bravais
> lattice vectors defined by (a/2,-b/2,0),  (a/2,b/2,0), (0,0,c). Instead I 
> get
> the space group  P2_1/m (#11). Most probably I am overlooking something
> obvious, but I can't figure out what. Suggestions are welcome :)
> 
> #Definition of the unit cell
> acell 5.39 11.1034 9.3247
> 
> rprim  0.5  0.5  0.0   # primitive vectors 
>       -0.5    0.5  0.0
>        0.0    0.0  1.0
> 
> #Definition of the atom types
> ntypat 1      # No of atom types
> znucl 92
> 
> #Definition of the atoms
> natom 2               # No of atoms in the cell
> typat 1 1              # Type of each atom
> 
> xred
>     0.10 -0.10    -0.25
>    -0.10  0.10     0.25
> 
> #Definition of the planewave basis set
> ecut 35      
> pawecutdg 40
> 
> #Exchange-correlation functional
> ixc 11 #GGA (PBE)
> 
> #Definition of the k-point grid
> kptopt 1
> 
> ngkpt 2 2 2
> tsmear 0.001
> 
> #Spin polarization
> nsppol 1
> 
> #Definition of occupation numbers
> occopt 3
> nband 40
> 
> #Definition of the SCF procedure
> nstep 100
> usepaw 1
> toldfe 1.0d-6
> iscf 7