[Pw_forum] how to relax the atoms position without changing the cell parameters

[Axel Kohlmeyer]

On Thu, 10 Jul 2008, lan haiping wrote:

LH> Why not to read the Document and related INPUT ?

please read e-mails a little bit more carefully
before responding and giving potentially incorrect
advice. it mentions a simple cubic crystal with
a benzene molecule on each position, so it is 
not about a simple molecule optimization.

the problem for these systems is actually, that
with DFT you get too _little_ interaction between 
the benzene molecules (except at high pressure, 
of course) due to the incomplete description of 
dispersion interactions...

cheers,
    axel.

LH> If you just want to do a simple relaxation for a molecule , two 
LH> points
LH> should be
LH> taken into attention :
LH> 1, The cell should be large enough to avoid image intetactions.
LH> 2, gamma sampling for BZ

LH> P.S , please supply your affiliation

On Wed, Jul 9, 2008 at 11:52 PM, ËïÑô <sunyang198498 at gmail.com> wrote:

> Hi!
> how could I relax the atoms position without changing the cell parameters
> say, if i have a simple cubic cell with each point having a benzene
> structure. How could I relax the benzene's atoms, say, hydrogen and
> carbon with the fixed edge size within the simple cubic cell.
>
> Thank you,
>
> Yang
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>



-- 
Hai-Ping Lan
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping at gmail.com, hplan at pku.edu.cn


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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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