<html><body><div style="color:#000; background-color:#fff; font-family:Arabic Transparent, Arial;font-size:12pt"><div dir="ltr"> Dear Xirainbow:<br>Thank you very much for your reply.<br>What is "relax of phonon calculation?<br>My purpose was the relax calculation before doing calculation of frequency.<br><br><br>Message: 1Date: Sun, 2 Jun 2013 19:07:20 +0800<br></div><div dir="ltr">From: xirainbow <<a href="mailto:nkxirainbow@gmail.com">nkxirainbow@gmail.com</a>><br></div><div dir="ltr">Subject: Re: [Pw_forum] phonon calculation<br></div><div dir="ltr">To: Banafshe Noori <<a href="mailto:b_noori88@yahoo.com">b_noori88@yahoo.com</a>>, PWSCF Forum<br></div><div dir="ltr"> <<a href="mailto:pw_forum@pwscf.org">pw_forum@pwscf.org</a>><br></div><div dir="ltr">Message-ID:<br></div><div dir="ltr"> <<a
href="mailto:CABBv2WJG3M5aiQc_nsSi6BcebE4oF2_yop42qNEs0Jrz-9vJ1Q@mail.gmail.com">CABBv2WJG3M5aiQc_nsSi6BcebE4oF2_yop42qNEs0Jrz-9vJ1Q@mail.gmail.com</a>><br></div><div dir="ltr">Content-Type: text/plain; charset=ISO-8859-1<br></div><div dir="ltr"><br></div><div dir="ltr">Dear Banafshe Noori :<br></div><div dir="ltr"><br></div><div dir="ltr">> can i use of press_conv_thr for a relax of phonon calculation?<br></div><div dir="ltr"> What is "relax of phonon calculation"? You can even do<br></div><div dir="ltr">phonon with experimental crystal lattices and atomic positions without<br></div><div dir="ltr">any relaxation.<br></div><div dir="ltr"><br></div><div dir="ltr">> and why the stress on my system is too high?(-40kbar)<br></div><div dir="ltr"> Take the output structure of pw.x as an input and relax it<br></div><div dir="ltr">again and again.<br></div><div
dir="ltr"><br></div><div dir="ltr">> What parameters do I need to be changed to reduce stress?<br></div><div dir="ltr"> Reduce press_conv_thr.<br></div><div dir="ltr"><br></div><div dir="ltr">On Sun, Jun 2, 2013 at 2:36 PM, Banafshe Noori <<a href="mailto:b_noori88@yahoo.com">b_noori88@yahoo.com</a>> wrote:<br></div><div dir="ltr">> Dear Xirainbow<br></div><div dir="ltr">><br></div><div dir="ltr">> thank alot for your respond.<br></div><div dir="ltr">><br></div><div dir="ltr">> I search in the input file of pwscf and saw that the is applied for a<br></div><div dir="ltr">> vc-relax calculation.<br></div><div dir="ltr">> can i use of press_conv_thr for a relax of phonon calculation?<br></div><div dir="ltr">> and why the stress on my system is too high?(-40kbar)<br></div><div dir="ltr">> What parameters do I need to be changed to reduce stress?<br></div><div
dir="ltr">><br></div><div dir="ltr">><br></div><div dir="ltr">><br></div><div dir="ltr">><br></div><div dir="ltr">><br></div><div dir="ltr">> Dear Banafshe Noori :<br></div><div dir="ltr">> press_conv_thr is the parameter to control the final stress.<br></div><div dir="ltr">> The default value for press_conv_thr is 0.5D0 Kbar, which<br></div><div dir="ltr">> is good enough for most condition.<br></div><div dir="ltr">><br></div><div dir="ltr">> On Sat, Jun 1, 2013 at 11:45 PM, Banafshe Noori <<a href="mailto:b_noori88@yahoo.com">b_noori88@yahoo.com</a>> wrote:<br></div><div dir="ltr">>> Dear all<br></div><div dir="ltr">>><br></div><div dir="ltr">>> I want to calculate phonon frequency. I did a relax for my system(carbon<br></div><div dir="ltr">>> nanotube) and saw that the stress (Kbar) for this
system is around<br></div><div dir="ltr">>> (-40Kbar). How can i decrease the stress on my system, and for an<br></div><div dir="ltr">>> acceptable<br></div><div dir="ltr">>> magnitude of ferquencey, how much be the stress on system.?<br></div>>></div></body></html>