[QE-users] vc-relax with PBE0 or HSE is not converging

[Giuseppe Mattioli]

Dear Salma
I don't know how outdated it is, but there is a README in the  
directory of the EXX examples

/path_to_QE_7.2/PW/examples/EXX_example

reporting this:

  WHAT PROPERTIES CAN I COMPUTE ?
   Energy and forces (thanks to Hellmann-Feynman theorem forces do not
   require extra calculations). In principle also stresses but the
   corresponding formulas have not yet been coded. <-------!!!!!!!
   So structural optimization is OK if the cell shape is kept fixed.

HTH
Giuseppe


Quoting NAIMI SALMA <salma_naimi at um5.ac.ma>:

> Dear all,
>
> I'm doing a vc-relax for my material with hybrid functionals and  
> ONCV pseudopotentials.
>
> When the job is done I can't find the optimized final coordinates  
> and lattice parameter in the output file , also I noticed that the  
> final pressure is positive and not close to zero, as bellow:
>
>      Computing stress (Cartesian axis) and pressure
>
>           total   stress  (Ry/bohr**3)                   (kbar)      
> P=      106.49
>    0.00072391  -0.00000000   0.00000000          106.49       -0.00   
>       0.00
>   -0.00000000   0.00072391   0.00000000           -0.00      106.49   
>       0.00
>   -0.00000000  -0.00000000   0.00072391           -0.00       -0.00   
>     106.49
>
>
>  I repeated the calculation so many times by modifying some input   
> variables but the same problems always occur for PBE0 and HSE as well.
>
>
> Before the last lines in the output file I find this:
>
>
>
> ...
>
> Input lattice vectors:
>
>     -0.50342437     0.00000000     0.50342437
>
>      0.00000000     0.50342437     0.50342437
>
>     -0.50342437     0.50342437     0.00000000
>
> New lattice vectors in INITIAL alat:
>
>     -0.50342437     0.00000000     0.50342437
>
>      0.00000000     0.50342437     0.50342437
>
>     -0.50342437     0.50342437     0.00000000
>
> New lattice vectors in NEW alat (for information only):
>
>     -0.50000000     0.00000000     0.50000000
>
>      0.00000000     0.50000000     0.50000000
>
>     -0.50000000     0.50000000     0.00000000
>
> Discrepancy in bohr =     0.000000    0.000000    0.000000
>
>
>      The maximum number of steps has been reached.
>
>
>      End of BFGS Geometry Optimization
>
>      new unit-cell volume =    382.92325 a.u.^3 (    56.74337 Ang^3 )
>
>      density =      5.57333 g/cm^3
>
>
> CELL_PARAMETERS (alat= 11.44879234)
>
>   -0.503424371   0.000000000   0.503424371
>
>    0.000000000   0.503424371   0.503424371
>
>   -0.503424371   0.503424371   0.000000000
>
>
> ATOMIC_POSITIONS (crystal)
>
> ....
>
>
>
> Where this problem is coming from please and how can I fix it?
>
> I attached my input file
>
>
>
>
>
>
>
> ------------------------------------------------------------
> Salma NAIMI
> PhD student - Mohamed 5 University-Rabat



GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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E-mail: <giuseppe.mattioli at ism.cnr.it>