[QE-users] phonons with vdW functional

[Aleksandra Oranskaia]

I will be very thankful for any thoughts on this issue.
Also if you know QE experts please kindly redirect the message.


> On Nov 26, 2018, at 6:05 PM, Aleksandra Oranskaia <aleksandra.oranskaia at kaust.edu.sa> wrote:
> 
> Hello dear users and developers of QE,
> 
> I am trying to calculate phonons using very good structure (tightly optimized, matching the experimental one, etc), but whatever I do the result is:
> 
>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>      Error in routine cdiaghg (448):
>      S matrix not positive definite
>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> 
> I varied:
> - number of processors (with too large # of processors similar issues are reported)
> - ecutrho increasing it up to ecutwfc*15
> - different smearings schemes (the system is a narrow band gap semiconductor)
> - different diagonalization procedures (from my personal experience: david fail sometimes where cg saves the day)
> - used nosym=.true.
> 
> I would highly appreciate any thoughts on the nature of this mistake happening in the very beginning of phonon calculation.
> 
> 
> Best,
> Alex.
> ___
> Aleksandra Oranskaia (M.Sc.)
> ChemS PhD student, KAUST
> Phone: +966 50 1335254
> 
> 
> 
> 
> 
> 


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