[Pw_forum] lattice parameter in 'vc-relax' mode doesn't change

[Sokseiha Muy]

I see. Thank you very much for your help.

Best,
Sokseiha.
________________________________
From: pw_forum-bounces at pwscf.org [pw_forum-bounces at pwscf.org] on behalf of Vincenzo Verdolino [vincenzo.verdolino at gmail.com]
Sent: Tuesday, August 19, 2014 12:58 PM
To: PWSCF Forum
Subject: Re: [Pw_forum] lattice parameter in 'vc-relax' mode doesn't change


As Paolo was mentioning I would suggest you to

grep -A 3 'CELL_PARAMETERS' output.out

you should get something like

CELL_PARAMETERS (alat= 22.67671359)
   0.971595358  -0.004204137   0.034718207
  -0.003973715   0.993274472  -0.003814071
   0.073550426  -0.008394064   2.103660061
--
CELL_PARAMETERS (alat= 22.67671359)
   0.971710425  -0.004267871   0.034659977
  -0.004044929   0.992889770  -0.003977620
   0.073404775  -0.008729724   2.103161050
--
CELL_PARAMETERS (alat= 22.67671359)
   0.971566286  -0.004317083   0.035948125
  -0.004085492   0.992305284  -0.003891887
   0.076105646  -0.008563323   2.103332063
--

as you see alat is constant because it's the starting value but parameters (ptimitive vector) change

you should be able to get back the cell parameter in the form A= , B= , C= , cosAB= , cosAC =, cosBC=

vincenzo


On Tue, Aug 19, 2014 at 11:28 AM, Paolo Giannozzi <paolo.giannozzi at uniud.it<mailto:paolo.giannozzi at uniud.it>> wrote:
On Sun, 2014-08-17 at 02:33 +0000, Sokseiha Muy wrote:

> I'm using QE to study the properties of BaF2 which is a cubic
> material. I notice that when I used the option 'vc-relax' to optimized
> my structure, in the output the volume of the unit cell change as
> expected but the lattice parameter is the same for every step.

the lattice parameter is set to its starting value. It is the length
of the primitive vectors that changes. Look for the primitive vectors
in the output: they are reprinted in various places and formats.

P.
--
Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216<tel:%2B39-0432-558216>, fax +39-0432-558222<tel:%2B39-0432-558222>

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