[Pw_forum] Question about Young's modulus

[Stefano de Gironcoli]

for a 2-D system I guess that the definition of stress will involve the 
area and not the volume ...
stefano


Mahdi Mirnezhad wrote:
> Dear Developers,
> I think there is a problem in the calculation of stress in Quantum
> Esperesso. This problem concern with the volume of unit cell. For bulk
> structures there is no problem for determination of Volume but in the
> super cell method code calculate stress according to unit cell volume
> so when i calculate Young's Modulus for graphene with two method
> (strees/strain or (E=(1/V)*second derivative of energy) ) i get
> different answer.
> What is your suggestion?
> Thanks for your reply.
>
> Mahdi  Mirnezhad
> Msc student of Mechanics
> Guilan University.
>
>
>
> On 10/7/10, Mahdi Mirnezhad <mirnezhad.mm at gmail.com> wrote:
>   
>> Dear all,
>> I calculated Young's modulusfor graphene and i got correct answer but
>> when I want to calculate Young's modulus for CNT(3,3) for a axial
>> strain with the same condition (same PS) i got a wrong answer?
>> Any suggestion appreciated,
>> tanks
>>
>> mahdi mirnezhade
>>
>>     
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