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<div class="moz-cite-prefix">the stress in the code is defined as
the derivative of the energy per unit volume with respect to
infinitesimal deformations<br>
sigma_alpha,beta = 1/Omega partial E / partial epsilon_alpha,beta<br>
for a deformation such that <br>
r_alpha -> r'_alpha = r_alpha + sum_beta epsilon_alpha,beta
r_beta<br>
it is symmetric in alpha,beta because the antisymmetric components
of the deformation (describing rotations) do not change the
energy.<br>
<br>
If I understand correctly the stress definitions
(<a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/Stress_measures">https://en.wikipedia.org/wiki/Stress_measures</a>) for infinitesimal
deformations they are all the same <br>
because J=1, F=I, dn_0=dn, ... etc<br>
<br>
If you are considering finite deformations the stress is the
derivative taken w.r.t. the present deformed configuration so I
think must be the Cauchy stress because the code does not know you
want to take another configuration as reference.<br>
Therefore, should be something like S = J (F^-1) sigma (F^-1)^T
<br>
<br>
HTH<br>
<br>
stefano<br>
<br>
<br>
<br>
On 17/02/2017 16:27, Mahdi Faghihnasiri wrote:<br>
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cite="mid:CAMGuPKR+qZx1EWTvVHjz3DLDv3mj84+SUioSFUEKtzc_sgf0Cg@mail.gmail.com"
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<pre>Dear all,
I know If I set tstress=.true. the stress tensor will be computed and
printed. but What's the kind of the Stress Tensor QE dose print? for example Cauchy,
true, Kirchhoff, PK2, ...
I am trying to calculate second Piola–Kirchhoff (PK2) stresses with QE. Any suggestions or comments are appreciated.
Sincerely
Mahdi<span class="">
</span></pre>
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<div dir="ltr"><span style="color:rgb(153,153,153)"><span
style="font-family:verdana,sans-serif"><b>Mahdi
FaghihNasiri</b></span></span><span><font
color="#888888"><br
style="font-family:verdana,sans-serif">
</font></span><span><font color="#888888">Department
of Physics<br>
Shahrood University of Technology<br>
Shahrood,<span
style="font-family:verdana,sans-serif"> Iran</span><font
color="#888888"><b><span
style="font-family:verdana,sans-serif"></span></b></font></font></span></div>
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