[Pw_forum] Problems computing Cholesky decomposition

[Gabriele Sclauzero]

Dear Fedai,

fedai inanir wrote:
> Dear all,
> 
> I am trying to run nanotribology computations for a 24-atom 
> graphene-like cluster on monolayer graphene of a 7x7 supercell. However, 
> execution of the code leads to an error message: "Problems computing 
> Cholesky decomposition". I looked up for this in the forum. I tried the 
> recommendations I found out but none of them worked. I also tried 
> diagonalization='david-serial' in the ELECTRONS namespace. I would be 
> delighted if someone has any suggestions to solve this problem.
> 
> /
> 
> &SYSTEM
> 
> ibrav = 4,
> 
> celldm(1) = 32.5350,
> 
> celldm(3) = 0.2,
> 
> nat = 152,
> 
> ntyp = 1,
> 
> ecutwfc = 32.0 ,


> 
> ATOMIC_SPECIES
> 
> C 12.01000 C.pz-rrkjus.UPF
> 

You are using an ultrasoft pseudopotential, hence you need to specify a cutoff for the 
charge density as well, ecutrho > 4*ecutwfc. People choose ecutrho ~ 8*ecutwfc, but it is 
usually good habit to check convergence when you start using a pseudopotential file.


Anyway the problem is in your input atomic coordinates, I think. The atoms at 
z=6.670736000 are too close to those at x=0. Remember that the code uses PBCs in all three 
directions! Probably you need to change celldm(3) to a more suitable value.
Try to visualize your system with xcrysden before repeating the calculation.

Also I would suggest to start with simpler examples and get used to the code input/output 
before moving to systems with hundreds of atoms.


Regards,

Gabriele

>  
>  
> Dr. Fedai Inanir
> Rize University
> Deparment of Physics
> Rize
> Turkey
>  
> 
> 
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