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<body class='hmmessage'><div dir='ltr'>Dear Paolo,<br><br>Thanks a lot for a prompt reply. I am bit confused since i started with tetragonal structure (ibrav=6) so i would have imagined that <span style="font-weight: bold;">a=b</span> would have been enforced by the code in case symmetry is conserved during optimization ...<br>but just to understand the answer fully, you are saying that these results don't represent physical pressure-induced tetragonal to orthorhombic transition but just a numerical artificat ?<br><br>I will really appreciate a clarification..<br><br>cheers,<br>Saqib Javaid<br>NCP, Pakistan.<br><br><br><div>> From: paolo.giannozzi@uniud.it<br>> To: pw_forum@pwscf.org<br>> Date: Fri, 14 Jun 2013 10:43:36 +0200<br>> Subject: Re: [Pw_forum] change of crystal symmetry during vc-relax calculations with pressure<br>> <br>> On Fri, 2013-06-14 at 07:18 +0000, saqib javed wrote:<br>> <br>> > Can vc-relaxation at a given pressure with bfgs method allows for<br>> > change of crystal symmetry ?? <br>> <br>> no, but only the symmetry as found by the code is conserved;<br>> "accidental" symmetries, e.g. lattice vectors a and b having <br>> equal length but no symmetry operation sending a into b, may <br>> be easily lost due to numerical noise.<br>> <br>> Paolo<br>> -- <br>> Paolo Giannozzi, Dept. Chemistry&Physics&Environment, <br>> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br>> Phone +39-0432-558216, fax +39-0432-558222 <br>> <br>> _______________________________________________<br>> Pw_forum mailing list<br>> Pw_forum@pwscf.org<br>> http://pwscf.org/mailman/listinfo/pw_forum<br></div> </div></body>
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