The ABINIT Users Mailing List ( CLOSED )

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

Glad that it works. It's not so "strange", though---internally abinit applies 
one element of acell to an entire vector of rprim. In the cases where 
different acell's are combined, as in body, face, and base centered 
tetragonal and orthorhombic, you get primitive vectors like (-a/2,0,c/2) and 
so forth--in these cases, there is no single element of acell that is a 
common factor, therefore the only choice is to set acell to 1.0 and then 
carry a, b, and c directly in rprim. 

 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: TORUMBA Doru 218423 <doru.torumba@cea.fr>
> To: forum@abinit.org
> Sent: Tuesday, December 9, 2008 10:07:02 AM
> Subject: RE: [abinit-forum] alpha-U structure
> 
> Dear Joe,
> 
> Thank you very much for the tip! Strange enough, but it works! 
> 
> Best regards,
> Doru
> 
> 
> > -----Original Message-----
> > From: Josef W. Zwanziger [mailto:jzwanzig@jzwanzig.org]
> > Sent: Tuesday, December 09, 2008 2:54 PM
> > To: forum@abinit.org
> > Subject: Re: [abinit-forum] alpha-U structure
> > 
> > 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 
> > > 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