<div dir="ltr"><div dir="ltr">On Sat, Jul 6, 2019 at 11:31 AM Carlo Nervi <<a href="mailto:carlo.nervi@unito.it">carlo.nervi@unito.it</a>> wrote:</div><div dir="ltr"><br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr"><div dir="ltr">I'd like to perform vc-relax calculations, but keeping strictly fixed the symmetry of the crystal.</div></div></div></blockquote><div><br></div><div>not sure I understand: if the starting structure has the desired crystal symmetry, the final structure will - apart from unfortunate or pathological cases - have the same symmetry</div><div><br></div><div>Paolo</div><div><br></div><div><br></div><div> <br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div>I supposed that the keyword</div><div>cell_dofree='volume'</div><div>should be the right option to use, but pw.x exit complaining that cell_dofree='volume' can be used only if ibrav=1.</div><div>Is there any technical reasons for this?</div><div>I was supposing that simply changing only celldm(1) should work.</div><div><br></div><div>I tried, as alternative, cell_dynamics='damp-w', which apparently keep almost the symmetry (but not strictly), but it shows an extremely slow convergence (in my molecular crystal vc-relax converge in 17 bfgs steps, while the damp-w vc-relax calculation is currently running the 127th step).</div><div><br></div><div>Thank you,</div><div>Carlo</div><div><br></div><div>P.S.: I suppose that simple deleting the below bold rows in cell_base.f90 (subroutine init_dofree) would not work..</div><div><br></div><div><div> CASE ( 'volume' )</div><div> !CALL errore(' init_dofree ', &</div><div> ! ' cell_dofree = '//TRIM(cell_dofree)//' not yet implemented ', 1 )</div><div> <b> IF ( ibrav /= 1 ) THEN</b></div><div><b> CALL errore('cell_dofree', 'Isotropic expansion is only allowed for ibrav=1; i.e. for simple cubic', 1)</b></div><div><b> END IF</b></div><div> iforceh = 0</div><div> iforceh(1,1) = 1</div><div> iforceh(2,2) = 1</div><div> iforceh(3,3) = 1</div><div> isotropic = .TRUE.</div><div><br></div>-- <br><div dir="ltr" class="gmail-m_-114926895268981870gmail_signature"><div dir="ltr"><pre>------------------------------------------------------------
Prof. Carlo Nervi <a href="mailto:carlo.nervi@unito.it" target="_blank">carlo.nervi@unito.it</a> <a>Tel:+39</a> 0116707507/8
Fax: +39 0116707855 - Dipartimento di Chimica, via
P. Giuria 7, 10125 Torino, Italy. <a href="http://lem.ch.unito.it/" target="_blank">http://lem.ch.unito.it/</a><br></pre></div></div></div></div></div></div>
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