<div dir="ltr">You are not using K points, so you will need a 2x2x2 cell to get something sensible.<div><br></div><div>Matt<br><br>On Thursday, August 8, 2019 at 11:54:20 AM UTC+1, Pierre Cazade wrote:<blockquote class="gmail_quote" style="margin: 0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex;">
<div text="#000000" bgcolor="#FFFFFF">
Hi Matt,<br>
<br>
Thanks for the tip about the cell_ref, I'll give it a try.
Otherwise, I define the symmetry and I keep it fixed. I also keep
the angles fixed for the first optimization.<br>
<br>
A new calculation I've just run with the DFT parameters from Dirk's
input file yields similar results as I obtained before:<br>
<br>
CELL| Vector a [angstrom]: 4.251 0.000 0.000 |a|
= 4.251<br>
CELL| Vector b [angstrom]: 0.000 7.405 0.000 |b|
= 7.405<br>
CELL| Vector c [angstrom]: -2.287 0.000 5.298 |c|
= 5.771<br>
<br>
I started with this however:<br>
<br>
&CELL<br>
ABC [angstrom] 5.078 6.192 5.387<br>
ALPHA_BETA_GAMMA [deg] 90.00 113.35 90.00<br>
SYMMETRY MONOCLINIC<br>
PERIODIC XYZ<br>
&END CELL<br>
<br>
I know from VASP the optimized unit cell is:<br>
<br>
a b c alpha
beta gamma<br>
5.12269 6.41270 5.41981 90.0000 112.7275 90.0000<br>
<br>
Of course, I do not expect two different software using different
methods and different pseudopotentials to give the exact same result
but they should be close enough. The contraction of the A vector and
the expansion of the B vector are absurd. I will try the ref_cell,
it might help.<br>
<br>
Regards,<br>
Pierre<br>
<br>
<br>
<div>On 08/08/2019 11:38, Matt W wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Standard inputs are in Angstroms for a coord
section.
<div><br>
</div>
<div>The most common problem is that the planewave basis changes
as the cell optimizes. You can use a constant size of plane
wave basis by specifying a reference cell, something like
this. Where the CELL_REF contains a reference cell that should
be a bit bigger that the expected largest cell after
optimization.</div>
<div><br>
</div>
<div>
<pre style="padding:0.7em 1em;font-family:Consolas,"Andale Mono WT","Andale Mono","Bitstream Vera Sans Mono","Nimbus Mono L",Monaco,"Courier New",monospace;font-size:14px;direction:ltr;background-color:rgb(251,250,249);color:rgb(51,51,51);border-radius:2px;overflow:auto;border-width:1px;border-style:solid;border-color:rgb(204,204,204)"> &CELL
ABC 5.620 5.620 5.620
&CELL_REF
ABC 5.620*1.1 5.620*1.1 5.620*1.1
&END
&END CELL</pre>
If your cell has symmetry (orthorhombic, hexagonal etc) you
can specify this to be kept. Similarly first optimizing just
the volume and keeping the angles constant, then relaxing
everything can be more efficient.</div>
<div><br>
</div>
<div>Also I'd stick with BFGS rather than LBFGS unless you
system is huge (> 2000 atoms)</div>
<div><br>
</div>
<div>Maybe this helps a little, </div>
<div><br>
</div>
<div>Matt</div>
<div><br>
</div>
<div><br>
</div>
<div>On Thursday, August 8, 2019 at 10:46:18 AM UTC+1, Dr. Dirk
Buddensiek wrote:
<blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">
<p><span style="color:windowtext">Hi Pierre,</span></p>
<p><span style="color:windowtext">good luck. Concerning
distance units:
It might be that there are in Bohr for MP2. But you
can set the units
explicitly in the input deck.</span></p>
Dirk<br>
<br>
Am Mittwoch, 7. August 2019 17:05:56 UTC+2 schrieb
Pierre-André Cazade:
<blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">Hello,
<div><br>
</div>
<div>I am rather new to CP2K though I am experienced
with molecular modelling both quantum and classical,
and with a wide range of software. It is quite
frustrating that it seems impossible to get CP2K to
perform a simple CELL_OPT of a beta glycine crystal
(20 atoms, monoclinic) with PBE. Such a calculation
works fine with VASP, so I am quite surprised the
same calculation goes astray with CP2K. Basically,
the B unit cell vector increases drastically up to
absurd values. Needless to say, this is a test
system as I wish to use CP2K for its linear scaling
DFT to model protein crystals. I have tried to play
with CUTOFF and REL_CUTOFF in the MGRID section up
to 1400 and 80 respectively. I also tried GPW and
GAPW methods, all electrons or GTH pseudo. Nothing
works. Please, if anyone could have a look at the
attached input file "cell_opt_qm.inp" and point
what's wrong in it, I would be grateful.</div>
<div><br>
</div>
<div>Furthermore, I have tried LS approach with DFTB
on a 5x5x5 crystal of beta glycine and do not have
much more success. First, the pressure in the
crystal is insanely high and will lead again to a 20
folds increase of the lattice vectors (with CG).
Then, with LBFGS method, the system stops after 3 to
4 cycles with a message telling LBFGS convergence
criteria were reached, whereas the system is clearly
not. Again, I would be grateful if anyone could tell
me what's wrong with my system ("cell_opt2_qm.inp"
with "betacry.pdb" for the coordinates). Ideally, my
goal would be to be able to run large complex
systems with the LS approach and with any DFT/DFTB
method.</div>
<div><br>
</div>
<div>Thank you in advance for your help.</div>
<div><br>
</div>
<div>Regards,</div>
<div>Pierre</div>
</div>
</blockquote>
</div>
</blockquote>
</div>
</div>
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<br>
<pre cols="72">--
Dr Pierre Cazade, PhD
AD3-023, Bernal Institute,
University of Limerick,
Plassey Park Road,
Castletroy, co. Limerick,
Ireland</pre>
</div>
</blockquote></div></div>