Dear Stefano,<br>Thanks for yr kind reply. For calculating the elastic constant i am refering the following paper.<br><br>
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--></style><font size="2">S K R
Patil et. al Phys.
Rev. B </font><font size="2"><b>73</b></font><font size="2">, 104118
(2006).<br><br>So in this paper, they generally fit a parabola equation in terms of energy as a function of strain and thus finds the C11, C12 and C44 etc. <br>But as u suggested to find the C11 etc at different volume, but change in volume cause the change in pressure. So the minimum of the parabola is not minimum at high pressure.<br>
<br><br>So i need an equation like Murnaghan equation of state, in which the the pressure derivative is included.<br></font><br><br> <br><div class="gmail_quote">On Tue, Jun 22, 2010 at 4:32 PM, Stefano Baroni <span dir="ltr"><<a href="mailto:baroni@sissa.it">baroni@sissa.it</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div style="">1) Calculate C11, C12, and C44 for different volumes<br><div><div>2) Calculate numerically their volume derivatives</div>
<div>3) Use the chain rule to express the pressure derivatives in terms of the volume derivatives</div><div>hope this helps - Stefano B</div><div><div></div><div class="h5"><div><br></div><div>On Jun 22, 2010, at 11:39 AM, Bipul Rakshit wrote:</div>
<br></div></div><blockquote type="cite"><div><div></div><div class="h5">Dear PWSCF user,<br>I want to calculate the pressure derivative of elastic constant for some of my cubic materials (ScP, ScN in NaCl phase). Please anybody tell me the procedure or refer any paper, where i get the method of calculating the pressure derivative of elastic constants (C11, C12, C44)<br>
<br><br>regards<br clear="all"><br>-- <br>Bipul Rakshit<br>Research Fellow,<br>S N Bose Centre for Basic Sciences,<br>Salt Lake,<br>Kolkata 700 098<br>India<br></div></div>
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<br></blockquote></div><br><br clear="all"><br>-- <br>Dr. Bipul Rakshit<br>Research Associate,<br>S N Bose Centre for Basic Sciences,<br>Salt Lake,<br>Kolkata 700 098<br>India<br>