[DFTB-Plus-User] Failure in diagonalisation routine zhegvd

[. Juita]

Dear Balint,

I tried to use "Eigensolver = RelativelyRobust {}" in the Hamiltonian block, as well as change the geometry with the coordinates which I obtained from the geometry optimisation result.  However, it stopped with the error message: "Failure in diagonalisation routine ZHEEVR, unable to complete Cholesky factorization of B    217".  It occured at the beginning of the geometry step 2.

Could you please suggest me how to solve the issue? Your assistance is greatly appreciated.
Thank you so much for your assistance.
Best regards,
Juita

________________________________________
From: DFTB-Plus-User <dftb-plus-user-bounces at dftb-plus.info> on behalf of Bálint Aradi <balint.aradi at bccms.uni-bremen.de>
Sent: 05 December 2013 16:52
To: User list for DFTB+ related questions
Subject: Re: [DFTB-Plus-User] Failure in diagonalisation routine zhegvd

Dear Juita,

On 12/05/2013 12:41 AM, . Juita wrote:
> Dear Users,
>
> I am the new user of DFTB+.  I tried the molecular dynamics simulations
> with the package, however, they stopped with error message "Failure in
> diagonalisation routine zhegvd, non-positive definite overlap!
> Minor      1 responsible".  The attached is the input file for the run.

If the error happens during the MD between two SCC iterations (so not
right at the beginning of a geometry step), then it is a problem with
the LAPACK-diagonalization routine we use per default. You can then try
the relatively robust instead by setting

Eigensolver = RelativelyRobust {}

in the Hamiltonian block.

If the error happens at the very beginning of a geometry step (1st SCC
cycle) then probably two atoms are too close to each other.

  Best regards,

    Bálint


--
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b_aradi/