[Pw_forum] Conversion of total energy to stress tensor

[Afshin Arjangmehr]

Dear Lorenzo,

Thank you very much. Surprisingly, I have considered tstress=.true. in my
calculations without knowing what exactly it does and as I reviewed my
output files, I found the stress matrix in Ry/bohr^3 (kbar).
I appreciate for your kind and helpful response once again.

Regards
Afshin

On Sun, Sep 25, 2016 at 11:33 PM, Lorenzo Paulatto <
lorenzo.paulatto at impmc.upmc.fr> wrote:

> Dear Afshin,
> it is not possible to convert total energy to stress; stress can be
> computed from the same ingredients (wavefunctions, self-consistent
> potential) as the total energy, but not just from the value of energy
> itself.
>
> pw.x can compute the stress of any give structure, you have to set
> "tstress=.true." in the &control namelist, but of course you have to do it
> before starting the calculation.
>
> kind regards.
>
> p.s. repeating your question every 8 hours won't increase the chance of
> getting an answer, especially on Sunday
>
> On 25 September 2016 at 17:49, Afshin Arjangmehr <ms.arjangmehr at gmail.com>
> wrote:
>
>> Dear QE developers and users,
>>
>> I have been able to calculate the total energy of crystalline structures
>> under various strain tensors using pwscf. Now I intend to convert the total
>> energy to stress tensors and then study the mechanical properties (either
>> elastic or plastic) of different materials under strain (I have seen
>> several papers that directly use E vs. Strain to calculate 2nd, 3rd, 4th,
>> ... elastic constants and find yield & ultimate stress, but I believe that
>> as Caro et al. http://dx.doi.org/10.1088/0953-8984/25/2/025803 mentioned,
>> using Stress-Strain curve produces much accurate results).
>> So, can anyone kindly give me some recommendation on how to convert Etot
>> to Stress tensor? or Is there any tool to do this conversion? , since
>> simply using (-dEtot/dVol) is not the solution
>>
>>
>> Regards
>>
>> --
>> With Best Regards
>> Afshin Arjhangemehr
>> PhD student in Radiation Application
>> Shahid Beheshti University G.C, Tehran, IRAN
>> (+98) 912 439 20 64
>>
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>>
>
>
>
> --
> Dr. Lorenzo Paulatto
> IdR @ IMPMC -- CNRS & Université Paris 6
> phone: +33 (0)1 44275 084 / skype: paulatz
> www:   http://www-int.impmc.upmc.fr/~paulatto/
> mail:  23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05
>
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>



-- 
With Best Regards
Afshin Arjhangemehr
PhD student in Radiation Application
Shahid Beheshti University G.C, Tehran, IRAN
(+98) 912 439 20 64
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