[Pw_forum] ibrav and celldm(4)

[Abolore Musari]

Dear Paulo, I dont understand what u mean by svn version and also want
to ask that does it mean that l cant use the cell parameters given by
Emine if yes pls can u give me another cell parameters l could use.
pls i would appreciate ur quick response. Thanks Abolore

On 6/27/11, Paolo Giannozzi <giannozz at democritos.it> wrote:
>
> On Jun 25, 2011, at 23:39 , Abolore Musari wrote:
>
>> alpha equal beta equal 90 degree
>
> beta = 90 ...
>
>> beta was gotten from reitveld refinement to be 113.81
>
> ...or beta = 113.81?
>
>> i dont know if my celldm(4) which is equal to cos(ab) should
>> be cos90 or cos113.81 or tell me the appropriate way to get
>> celldm(4)=cos(ab).
>
> the monoclinic (P? ibrav=12?) lattice can be described with
> unique (i.e. orthogonal to a) axis c, b axis at angle gamma /= 90
> with a; or with unique axis b, c axis at angle beta /= 90 with a.
> QE uses the former description; apparently you have found
> the latter description in the literature, so you have to either
> convert the latter into the former, or write down explicitly the
> crystal axis, or to use the latest svn version that allows for
> the latter description as well (ibrav=-12)
>
> P.
> ---
> Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
>
>
>
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