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

[Paolo Giannozzi]

The stress calculation with hybrid functionals is actually implemented, 
but there are still some mysterious problems. See: 
https://gitlab.com/QEF/q-e/-/issues/204

Paolo

On 6/14/23 15:46, Giuseppe Mattioli wrote:
> 
> 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 I don't know how outdated it is, but there is a README in the directory 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
> Via Salaria Km 29,300 - C.P. 10
> I-00015 - Monterotondo Scalo (RM)
> Mob (*preferred*) +39 373 7305625
> Tel + 39 06 90672342 - Fax +39 06 90672316
> E-mail: <giuseppe.mattioli at ism.cnr.it>
> 
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222