<div dir="ltr"><div><font> <span style="color:rgb(0,0,0);font-family:'Times New Roman';font-style:normal;font-variant:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br>
<font>Yue-Wen Fang</font></span><font><span style="color:rgb(0,0,0);font-family:'Times New Roman';font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);display:inline!important;float:none"><span class=""> </span></span>wrote on <i style="color:rgb(0,0,0);font-family:'Times New Roman';font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">Thu May 9 15:40:00 CEST 2013</i></font></font><br>
<br></div><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote"><div id=":1ec">
Dear all,<br>
<br>
when we need to make a relaxation of heterojunction (supercell, such as a<br>
system contains 40 atoms), *which one in the following choices is the best<br>
way?*<br>
*A:* full relaxation (volume shape, lattice constant and atomic positions<br>
vary)<br>
*B: * fix the lattice constant<br></div></blockquote><div><br></div><div> when you don't know the details of your system or it is not a common solid state system you should relax all the parameters. But if you know some little details of your system you can decrease the cost of variable-cell calculations. For instance if your system is a simple cubic with orthogonal vectors you can simply do some SCF calculation and plot E versus lattice constant to have an estimate of your cell parameter. Also it is not bad to use this cell constant as an input in a relaxation (not variable-cell one) process to find the optimized position of atoms. <br>
</div><div>In this way you may be known more about your system and it is easier to start a vc-relax calculation.<br><br></div><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote">
<div id=":1ec">
<br>
any other better relaxation manners is welcome<br>
thank you very much!<br></div></blockquote><div><br> <br></div><div> You can directly go to doing "vc-relax" and see whether the above procedure is less expensive or the current one ! let us know :) <br></div>
<div> </div><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote"><div id=":1ec">
<br>
--<br>
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Yue-Wen FANG, PhD candidate<br>
Key Laboratory of Polar Materials and Devices, Ministry of<br>
Education<<a href="http://clpm.ecnu.edu.cn/" target="_blank">http://clpm.ecnu.edu.cn/</a>><br>
East China Normal University <<a href="http://www.ecnu.edu.cn/english/" target="_blank">http://www.ecnu.edu.cn/english/</a>><br>
I will persist until I succeed!<br>
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</div></blockquote><div> <br><br><br> Best Wishes, m<br><br> <br> <br><br><br>
----------------------------------------<br>Masoud Nahali<br>SUT<br><a href="mailto:masoud.nahali@gmail.com" target="_blank">masoud.nahali@gmail.com</a> <br><a href="http://alum.sharif.edu/%7Em_nahali" target="_blank">alum.sharif.edu/~m_nahali</a> <br>
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