[Pw_forum] Young's Modulus

[mohsen modaresi]

Dear Eduardo Ariel Menendez Proupin,
At first i relaxed nano-tube and obtain the position of carbon atoms in the
ground state. Then i decrease the tube length. A in the relation is the area
of nano-tube (A=pi*R*R which R is the radius of tube). F is the atomic force
in the Z axis which can be calculated by using Q.E.
I think it is better to calculate total energy in some configuration and use
(F=dE/dz, where E is the total energy in different configuration).
Is there any problem in this procedure?



On Thu, Sep 23, 2010 at 12:58 AM, Eduardo Ariel Menendez Proupin <
eariel99 at gmail.com> wrote:

> Hi,
> I think we always know what WE do, but not all of what computers do :-(.
>
> Mohsen, did you relaxed the atoms after the compression? Why did you
> calculate force and not stress. Have you used a finite nanotube and computed
> the forces upon the atoms of the edge? Finally, how is defined A in   E=(F/A)/((L-L0)/L0)
> for the case of a single nonotube?
> Best regards
> Eduardo
>
> Eduardo Menendez
> Departamento de Fisica
> Facultad de Ciencias
> Universidad de Chile
> Phone: (56)(2)9787439
> URL: http://fisica.ciencias.uchile.cl/~emenendez<http://fisica.ciencias.uchile.cl/%7Eemenendez>
>
> Let's pray for the 33 trapped miners! Four months to rescue
>
>
>
>> ---------- Mensaje reenviado ----------
>>
>> From: Stefano Baroni <baroni at sissa.it>
>> To: PWSCF Forum <pw_forum at pwscf.org>
>> Date: Wed, 22 Sep 2010 19:43:15 +0200
>>
>> Subject: Re: [Pw_forum] Young's Modulus
>> For that, also LRT akkows one to know what one is doing ... ;-)
>> SB
>>
>> On Sep 22, 2010, at 7:30 PM, Mehmet Topsakal wrote:
>>
>> Dear Eyvaz,
>>
>> I think you omitted one more thing to mention. Brute-force method also
>> allows one to know what he is doing.
>>
>>
>>
>> On Wed, Sep 22, 2010 at 8:14 PM, Eyvaz Isaev <eyvaz_isaev at yahoo.com>
>> wrote:
>>
>>> Hi,
>>>
>>> Yes, you are right about Abinit for elastic constants calculations. The
>>> main question is which method (Abinit or via total energy) is easier
>>> and less time-consuming.
>>>
>>> Bests,
>>> Eyvaz.
>>> -------------------------------------------------------------------
>>> Prof. Eyvaz Isaev,
>>> Department of Physics, Chemistry, and Biology (IFM), Linkoping
>>> University, Sweden
>>> Theoretical Physics Department, Moscow State Institute of Steel & Alloys,
>>> Russia,
>>> isaev at ifm.liu.se, eyvaz_isaev at yahoo.com
>>>
>>
>>>
> --
>
>
> .
>
>
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>


-- 
Mohsen Modarresi,
PhD student of Solid State Physics, Ferdowsi University of Mashhad, Iran.
Phone +98-9133452131
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