[Pw_forum] rdiaghg error # 122 in Phonon Calculation

[Paolo Giannozzi]

On Monday 12 June 2006 20:09, Sigifredo Sanchez-Carrera wrote:

>      from rdiaghg : error #       122
>      info =/= 0

The paragraph in the users' guide about erros in cdiagh/cdiaghg
applies as well to this case.
---
Possible reasons:
 * serious error in data, such as bad atomic positions or bad crystal
    structure/supercell;                                              
 * a bad PP (for instance, with a ghost);
 * a failure of the algorithm performing subspace diagonalization.
    The LAPACK algorithms used by cdiagh or cdiaghg are very robust
    and extensively tested. Still, it may seldom happen that such  
    algorithms fail. In at least one case the failures was tracked
    to the non-positiveness of the S matrix appearing in the US-PP
    formalism. In other cases, the error is found to be non reproducible
    on different architectures and disappearing if the calculation
    is repeated with even minimal changes in its parameters.
    In both cases, the reasons for such behavior are unclear and
    the only advice is to use conjugate-gradient diagonalization
    (diagonalization='cg'), a slower but very robust algorithm, 
    and see what happens.
---
You checked that your atomic  positions make sense, didn't you?

Paolo
-- 
Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
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