[Pw_forum] monoclinic cell definition question

[Jonas Baltrusaitis]

It just became increasingly confusing. Say I will rotate a,b,c and alpha, beta, gamma and x,y,z. But then pwscf "gamma", e.g. cosab gets rotated, too, so this 90 degree angle from cif again ends up as cosab again which it can't be

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