[Wannier] *.mmn file format

[Arash Mostofi]

Dear Carlos

Let's say that a particular line in the nnkpts block of seedname.nnkp 
looks like

5  9  1  -1  0

The first integer tells us that we are considering kpoint number 5 in 
the list of kpoints given in the input file. Let's denote it by vector 
k. The second integer means that kpoint number 9 in the list of kpoints 
is a periodic image of the vector k+b. Note that the kpoint specified in 
the second column will always be in the first Brillouin zone, which is 
why the next three integers are there. They tell you which periodic 
image of the reciprocal cell the k+b that you actually want is in. In 
this example we have

(k+b)_actual = (k+b)_1BZ + 1*B_1 + (-1)*B_2 + 0*B_3

where (k+b)_1BZ is kpoint number 9 in the list of kpoints, and B_i are 
the reciprocal lattice vectors. Given that you know k and can work out 
(k+b)_actual as above, then calculating the b-vector itself is not so 
difficult. Alternatively, if you look into the source code, the array 
called "bk" directly contains the b_vectors for each k-point.

Hope that helps

Arash

-- 
:------------------------------------------------------------:
: Dr. Arash A. Mostofi           :: a.mostofi at imperial.ac.uk :
: Lecturer and RCUK Fellow       ::                          :
: Depts. of Materials & Physics  ::                          :
: Imperial College London        :: T  +44 (0)207 594 6753   :
: London SW7 2AZ, United Kingdom :: F  +44 (0)207 594 6757   :
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Carlos Reis wrote:
> Hello
> 
> I'm trying to calculate the spreads OmegaI, OmegaOD and OmegaD
> (equations 34, 35 and 36 of PRB 56, 12851) using the b vector list of
> the wannier90
> output file and the information contained in the *mmn file.
> 
> Are the blocks in this file ordered according to the order of the b vector list?
> 
> kpt1 b1
> kpt1 b2
> .
> .
> .
> kpt1 bn
> kpt2 b1
> kpt2 b2
> .
> .
> .
> kpt2 bn
> .
> .
> .
> .
> kptn' bn
> 
> I know that the file format is described in the User's Guide but I
> need to have a correspondence between a given block in this file and a
> given b vector but I don't think I understand how the list of 5
> integers prior to each block can give me that.
> 
> I'm sorry if this is a basic question. Any help will be appreciated.
> 
> Best regards, Carlos Reis.
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