<html><head></head><body><div class="yahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;"><div dir="ltr" data-setdir="false">Dear QE users</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">I am having a very basic question regading the way of defining the structure in QE. I am trying to understand the way of defining "cell parameter" section <span>when using the symmetry of the structure </span>in scf.in file of QE. <br></div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">For a fcc structure I saw in the pw.x definition that with ibrave=0 , we can define (I believe it is for primitive structure?)<br></div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">CELL_PARAMETER</div><div dir="ltr" data-setdir="false"><span><pre>a/2(-1,0,1) <br>a/2(0,1,1)<br>a/2(-1,1,0)</pre></span><div dir="ltr" data-setdir="false">My question is; can we also define this as below.</div><div dir="ltr" data-setdir="false"><div><span><pre>a/2(1,0,1) <br>a/2(0,1,1)<br>a/2(1,1,0)</pre></span></div><div dir="ltr" data-setdir="false">and does the order matters? ( I mean if I rotate this as below, does it requires any changes to the way I should give atomic positions? if so how to decide?)</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false"><span><span><pre>a/2(0,1,1)<br>a/2(1,0,1) <br>a/2(1,1,0)<br><br>Thank you<br>D.<br></pre></span></span></div><div dir="ltr" data-setdir="false"><div><span></span></div><div><br></div></div></div></div></div></body></html>