<div dir="ltr"><div>It is easier to figure out what the various "cell_dofree" options do from the code than from the documentation: look for routine 'init_dofree" in Modules/cell_base.f90 (iforceh(i,j)=0 means "keep component i of basis vector j fixed")<br><br></div>Paolo<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jul 25, 2017 at 12:19 PM, BARRETEAU Cyrille <span dir="ltr"><<a href="mailto:cyrille.barreteau@cea.fr" target="_blank">cyrille.barreteau@cea.fr</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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Thanks for your reply but I am still not very sure I understand well the difference between the two options:<span class=""><br>
'xy' : only v1_x and v2_y are moved<br>
'2Dxy' : only x and y components are allowed to change<br>
<br></span>
When the vectors v1 and v2 are not orthogonal (which is my case) the option 'xy' is not appropriate ?<span class=""><br>
<br>
Cyrille<br>
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<div style="font-family:Tahoma;font-size:13px"><b>Cyrille Barreteau</b><br>
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<div id="m_-8613939430854290551divRpF304973" style="direction:ltr"><font size="2" face="Tahoma" color="#000000"><b>De :</b> <a href="mailto:pw_forum-bounces@pwscf.org" target="_blank">pw_forum-bounces@pwscf.org</a> [<a href="mailto:pw_forum-bounces@pwscf.org" target="_blank">pw_forum-bounces@pwscf.org</a>] de la part de Thomas Brumme [<a href="mailto:thomas.brumme@uni-leipzig.de" target="_blank">thomas.brumme@uni-leipzig.de</a>]<br>
<b>Envoyé :</b> mardi 25 juillet 2017 11:32<br>
<b>À :</b> <a href="mailto:pw_forum@pwscf.org" target="_blank">pw_forum@pwscf.org</a><br>
<b>Objet :</b> Re: [Pw_forum] vc-relax & cell_dofree<br>
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<p>Dear Cyrille,</p>
<p><br>
</p>
<p>from the input description:<br>
<br>
'xy' : only v1_x and v2_y are moved<br>
<br>
'2Dxy' : only x and y components are allowed to change<br>
<br>
Thus, even in the case of cell_dofree='xy' I think the cell will change. Anyway, the deviation from 120 DEG is quite small (119.43 DEG if I'm not wrong) - I don't know if this could be do to numerical issues. Maybe try starting a new relaxation with a hexagonal
cell but smaller in-plane lattice vector of ~99.1%</p>
<p><br>
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<p>Cheerio</p>
<p><br>
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<p>Thomas<br>
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<div class="m_-8613939430854290551moz-cite-prefix">On 07/25/17 09:08, BARRETEAU Cyrille wrote:<br>
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Dear QE community<br>
<br>
I have a question related to vc-relax and the option cell_dofree.<br>
I want to relax a 2D metal-organic framework (MOF) with hexagonal lattice (ibrav=4)<br>
Could you please explain what is the difference between cell-dofree=xy and cell_dofree=2Dxy?<br>
<br>
I have noticed that when using cell_dofree=2Dxy the final CELL_PARAMETER is no longer perfectly hexagonal (see below). Should I use cell_dofree=xy instead and why?<br>
<br>
final:<br>
CELL_PARAMETERS (alat= 25.44640422)<br>
0.990921488 -0.000187347 0.000000000<br>
-0.495622997 0.858299558 0.000000000<br>
0.000000000 0.000000000 0.742630080<br>
<br>
Thanks in advance<br>
<br>
Cyrille<br>
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<div style="font-family:Tahoma;font-size:13px"><b>Cyrille Barreteau</b><br>
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<div style="font-family:Tahoma;font-size:13px"><font size="2"><font face="Times New Roman">CEA Saclay<span style="background-color:white"></span></font><font face="Times New
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</span></font>91191 Gif sur Yvette Cedex<span style="background-color:white"></span>, FRANCE
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Dr. rer. nat. Thomas Brumme
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