[DFTB-Plus-User] "Failure in diagonalisation routine dsygvd.." error

[Vinay Hegde]

Dear users and developers,

I am studying N_2 and CO_2 adsorption properties in a MOF using the
'znorg-0-1' parameter set. All bulk calculations ran fine but I am
facing a strange error when performing constrained geometry
optimization for the (001) surface with ~20 Angstrom of vacuum.
Interestingly, in all the different configurations (I have 12-15
different configurations of the molecule on the MOF), this error
occurs exactly (this is the only reason I called it a strange error)
at the 31st geometry step:

 ********************************************************************************
 ** Geometry step: 31
 ********************************************************************************

   iSCC Total electronic   Diff electronic      SCC error
 ERROR!
 -> Failure in diagonalisation routine dsygvd, non-positive definite
overlap! Minor   1091 responsible.

I have tried changing the mixing parameter, the mixer itself,
distorting the location of atoms a little and so on but the error
keeps occurring there: at the 31st geometry step.

I have attached my dftb_in.hsd file and the standard output with this
mail. I am using DFTB+ 1.2 and the precompiled binary for my
calculations.

Any suggestions or pointers are most welcome.

Regards,
Vinay

--

Vinay Ishwar Hegde
Graduate Student
Theoretical Sciences Unit (TSU)
Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR)
Jakkur, Bangalore 560 064
Email: vinayhegde at jncasr.ac.in
Phone: +91-96639-92336
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