[Wien] Space group 185 HoMnO3

[John Rundgren]

Many thanks to
	Gerhard Fecher
	Laurence Marks
	Caroline Roehr
	Peter Blaha
for advice concerning space group 185 and a .cif file with only four
decimal places.

Got a strong feeling that I should have understood expanding 0.3333 to
0.333333 - symmetry is exact is exact is exact - and that I should have
known what's in User's Guide. UG says at the end of Sec. 3.6 that one
can indeed write 1/3 as input to StructGen.
With best regards,
John

On Tue, 2010-01-12 at 20:32 +0100, Peter Blaha wrote:
> scan_cif.f even has a "patch" for inaccurate positions and
> checks if it should be 1/6, 1/3,...:
> 
>       if (f1.and.sseting.eq.'hexagonal') then
>          small=2.0d-5
>          do i=1,nat
>             do j=1,2
>                do jfract=1,5
>                   fract=jfract/6.d0
>                   if (abs(x(j,i)-fract).lt.small) x(j,i)=fract
>                   if (abs(x(j,i)+fract).lt.small) x(j,i)=-fract
> 
> However, at present it requires a precision of 2.d-5 and this is not 
> fulfilled when x=0.3333 only.
> 
> It is trivial to change and I'll do it, but:  what if you have a cif 
> file for a structure with a small distortion ??
> 
> 
> 
> John Rundgren schrieb:
> > Dear All,
> > When w2web is applied to HoMnO3.cif (space group 185, 30 atoms/UC), it
> > generates HoMnO3.struct (46 atoms/UC), see Attachments. The .struct
> > entries are,
> > O1 MULT=2
> > O2      12 (4 are correct, the rest are repetitions)
> > O3      6
> > O4      6
> > Mn      6
> > Ho1     2
> > Ho2     12 (4 are correct, the rest are repetitions).
> > 
> > As a consequence, CrysDen is embarrassed and goes terribly slow. When I
> > clean up HoMnO3.struct manually, XCrysden is quick as usual. 
> > 
> > However, when I make "initialize calc.", w2web goes back to the
> > incorrect structure. It starts calculating NN distances between Ho2 and
> > itself, which are, of course, equal to zero. Stop.
> > 
> > How can one make w2web understand HoMno3.cif ?
> > Thanks in advance,
> > John
> > 
> > 
> > 
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