[Pw_forum] Question on based-centered monoclinic cell input

[Paolo Giannozzi]

On Monday 10 October 2005 21:13, Yansun Yao wrote:

> I have a question on the input defining a based-centered monoclinic
> cell (ibrav=13) [..] In unit of alat, the latgen routine generates
>
>     cos(ab)   0    sin(ab)
>     cos(ab)   0   -sin(ab)
>       b/a    c/a    0
>    For a based centered cell, I expect the two vectors on the
> plane should be 1/2(a+b) and 1/2(a-b)?
>    Is the program expected a different setting?  If so, what
> is it?

the primitive lattice vectors used by the code are explained 
at the end of file Doc/INPUT_PW. The primitive lattice vectors 
for the base-centered monoclinic case look actually quite weird.
Maybe nobody ever used them. If you have a clear idea of what 
they should look like, please let us know. 

Note that you can input your lattice vectors by specifying
ibrav=0 and a card CELL_PARAMETERS

Paolo


-- 
Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
Scuola Normale Superiore    Phone:   +39/050-509876, Fax:-563513 
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