[Pw_forum] monoclinic cell definition question

[Jonas Baltrusaitis]

wait, but then it's not clear anymore what angles are between which axes...

Jonas


--- On Tue, 5/12/09, Michael Mehl <rcjhawk at gmail.com> wrote:

> From: Michael Mehl <rcjhawk at gmail.com>
> Subject: Re: [Pw_forum] monoclinic cell definition question
> To: jasius_1 at yahoo.com, "PWSCF Forum" <pw_forum at pwscf.org>
> Date: Tuesday, May 12, 2009, 5:40 PM
> Ah, but if you do that you'll have a left-handed
> coordinate system instead of a right-handed one.
> 
> To convert from "unique axis c" coordinates to
> "unique axis b" coordinates, and simultaneously
> maintain the handedness of the primitive vectors, take
> 
> a -> c
> b -> a
> c -> b
> 
> alpha -> gamma
> beta  -> alpha
> gamma -> beta
> 
> HOWEVER:  If you are in a base-centered monoclinic lattice,
> complications can ensue.  In that case, study the various
> options in the space group tables, and be very, very,
> careful, making sure that you have the chosen the correct
> vectors to define the base in relation to the unique axis.
> 
> A large number of the errors in the Lattice pages are
> because I wasn't careful about this.
> 
> 
> Jonas Baltrusaitis wrote:
> 
> > I just went through an example of monoclinic crystal
> structure
> http://cst-www.nrl.navy.mil/lattice/struk/g0_6.html
> > 
> > Seems like when compared with description in INPUT_PW
> b should be swapped with c and beta should be swapped with
> gamma (going from cif file to pwscf input)
> > 
> > Jonas
> > 
> > 
> 
> 
> -- Michael Mehl
> Naval Research Laboratory, Washington DC
> Author of http://cst-www.nrl.navy.mil/lattice (and other
> things)
> But I'm not at work now, so standard disclaimers apply