[QE-users] differently complied QE

[Nicola Marzari]

Last - note that 3.458 and 3.453 are really close - so the accuracy you 
have now is good enough for research purposes.

			nicola



On 08/01/2019 00:38, Nicola Marzari wrote:
> 
> 
> 
> Well, the numbers you get are not infinitely precise - there is
> a threshold where you stop minimizing forces and cell geometry,
> using forces and stresses that are not perfect because each SCF cycle is
> not converged to infinite perfection.
> 
> Bottom line - try to tighten all the convergencies (scf convergence
> at every cycle, and forces at every ionic relxations, and pressure...)
> 
> conv_thr for electrons
> etot_conv_thr for ions
> forc_conv_thr for ions
> press_conv_thr for cell
> 
> are the variables to play with. I would make sure conv_thr is very tight
> (10^-10 per atom, or even less) and then play with forc_ and press_
> 
>          nicola
> 
> 
> On 07/01/2019 14:24, Aleksandra Oranskaia wrote:
>> Hello dear users and developers of QE,
>>
>> I have recently noticed that one and the same QE version that was 
>> installed with different libraries, compilers, on different machines 
>> (with very different hardware) not only gives different total energies 
>> for the same inputs but also quite different optimized lattice 
>> constants (say, 3.458 versus 3.453 that does not seem no be acceptable).
>>
>> So the question is: how to know which installation accumulates some 
>> small(?) numerical problems?
>> In standard QE pw examples there is no example with variable-cell 
>> relaxation done on “ideally” installed code, so there is no reference 
>> point to reproduce.
>>
>>
>>
>> Best,
>> Alex.
>> ___
>> Aleksandra Oranskaia (M.Sc.)
>> ChemS PhD student, KAUST
>> Phone: +966 50 1335254
>>
>>
>>
>>
>>
>>
>>
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> 
> 


-- 
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project