<div dir="ltr">Dear José, the difference between "a" and "b" parameter is around of 0.0000000009 bohr, this values is not important. And your hexagonal symetries does not changes.<div><br></div><div>Best</div>
<div><br></div><div>PhD. Arles V. Gil Rebaza</div><div>Instituto de Física La Plata</div><div>La Plata - Argentina<br><div class="gmail_extra"><br><br><div class="gmail_quote">2014-08-16 22:13 GMT-03:00 José Gadelha da Silva Filho <span dir="ltr"><<a href="mailto:gadelha@fisica.ufc.br" target="_blank">gadelha@fisica.ufc.br</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>Dear QE users,</div><div><br></div><div>I am working with a hexagonal symmetry crystal and I relaxed all internal coordinates and cell parameters with vc-relax-bfgs algorithm.</div>
<div><br></div><div>I have some concern about my results. So, I would like some advice. </div>
<div><br></div><div>My initial cell parameter are:</div><div><br></div><div><br></div><div>45.48740530000000000<span style="white-space:pre-wrap"> </span>0.00000000000000000<span style="white-space:pre-wrap"> </span>0.00000000000000000</div>
<div>-22.74370265000000000<span style="white-space:pre-wrap"> </span>39.39324854203890000<span style="white-space:pre-wrap"> </span>0.00000000000000000</div><div>0.00000000000000000<span style="white-space:pre-wrap"> </span>0.00000000000000000<span style="white-space:pre-wrap"> </span>10.31035723491920000</div>
<div><br></div><div>with vectores 'a' and 'b', as:</div><div><br></div><div>a = b = 45.48740530000000000</div><div>c = 10.31035723491920000</div><div><br></div><div>After optimization I got this value:</div>
<div><br></div><div>44.53851082397360000<span style="white-space:pre-wrap"> </span>0.00000000000000000<span style="white-space:pre-wrap"> </span>0.00000000000000000</div><div>-22.26925541198680000<span style="white-space:pre-wrap"> </span>38.57148182127630000<span style="white-space:pre-wrap"> </span>0.00000000000000000</div>
<div>0.00000000000000000<span style="white-space:pre-wrap"> </span>0.00000000000000000<span style="white-space:pre-wrap"> </span>10.12292974744850000</div><div><br></div><div>In my calculation all operations symmetry are conserved. However if use the cell parameters as:</div>
<div><br></div><div>a = 44,53851082397360000</div><div>b = 44,53851082482830000</div><div>c = 10,12292974744850000</div><div><br></div><div>The 'a' and 'b' parameter aren't exactly the same.</div><div>
<br></div><div>I did a test, where I use</div><div><br></div><div>ibrav = 4</div><div>celldm(1)= 44.53851082397360000,</div><div>celldm(3) = 0.227284872 ,</div><div><br></div><div>The component forces of atoms become high than (>10-3). </div>
<div><br></div><div>To keep the component forces of atoms less than >10-3, I have to use ibrav = 0 and specify the matriz of cell parameters. </div><div><br></div><div>With this process, Can I still consider my cell as hexagonal symmetry?</div>
<div><br></div><div>Cheers</div><span class="HOEnZb"><font color="#888888"><div><br></div>-- <br><div dir="ltr">José Gadelha da Silva Filho<div><br></div><div>Aluno de Doutorado do Curso de Pós-Graduação em Física</div><div>
da Universidade Federal do Ceará.</div></div>
</font></span></div>
<br>_______________________________________________<br>
Pw_forum mailing list<br>
<a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br>
<a href="http://pwscf.org/mailman/listinfo/pw_forum" target="_blank">http://pwscf.org/mailman/listinfo/pw_forum</a><br></blockquote></div><br><br clear="all"><div><br></div>-- <br>###---------> Arles V. <---------###
</div></div></div>