[Wannier] Query on kmesh

[Jonathan Yates]

On 1 May 2012, at 22:39, Ajit Vallabhaneni wrote:

> Dear Users and developers,
> 
>          I am new to using W90 modules. I am trying to do some calculations on graphene using EPW (which uses wannier as a library).
> I did some calculations on a coarse mesh (6x6x1) successfully, when i repeated the same on a denser mesh (24x24x1), it was terminating with the following message
> 
> " Exiting.......
> kmesh_get_bvector: Not enough bvectors found". 
> 
> 
> I read a previous post which suggests to change the 'kmesh_tol' parameter. However, i am not quite sure it works from that post. Please let me know if there are any other suggestions.

Only use kmesh_tol as a last resort. And only use it if you understand what it does.
 
As I wrote to this list last weekend
 'Most problems with finding the k-point shells are caused by inaccurate lattice parameters or kpoints in the win file.'
So make sure you are giving those quantities accurately in the win file.

 Without more details (eg the win file) it is hard for me to give more specific guidance. However, you should know that if you set iprint=4 in the win file the kmesh routine will give you a lot more debugging information.



> --------------
> Cycle:      1
> wann_main: ZHEEV in internal_new_u_and_m failed, info=            3
>            trying Schur decomposition instead
> wann_main: SCHUR failed, info=            4
> Exiting.......
> wann_main: problem computing schur form 1
> 
> I havenot changed any input parameters ( I am using QE V4.0.3). Please let me know how to fix this issue. 

That is almost certainly a problem with the lapack / blas libraries you have linked to.

 Jonathan




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