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<p>cp2k prints "CELL| Vector" after each iteration of the optimizer.
From this you can calculate the lattice constant.</p>
<p>The lattice constant usually refers to the dimension of a unit
cell, therefore it does not change when you create a supercell.
The cell dimensions, however, differ between the unit and
supercell.</p>
<p>Fabian<br>
</p>
<div class="moz-cite-prefix">On 12.05.2021 13:42, sumit agrawal
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CALSDoYbEU_9OwK=MBiOjwBmbb6Lm+tiyRCKgtHxTNhK=V_g...@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">Dear Fabian,<br>
<div><br>
</div>
<div>Thanks for the quick response. Actually I prepared a
lattice structure (2x2x2) in VESTA software. Is it the correct
tool to prepare lattice structure, any idea? </div>
<div><br>
</div>
<div>I tried again to prepare a lattice structure. So 2x2x2 will
contain 32 atoms. Then I performed cell_opt in cp2k. I am
attaching my coordinate file, input file and out file. </div>
<div><br>
</div>
<div>Where will I find the lattice constant in the output file?</div>
<div><br>
</div>
<div>One more query: will the lattice constant for 1x1x1 unit
cell and nxnxn unit cell be same or different?</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Wed, May 12, 2021 at 1:57
PM Fabian Ducry <<a href="mailto:fabia...@gmail.com"
moz-do-not-send="true">fabia...@gmail.com</a>> wrote:<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>
<p>Dear Sumit</p>
<p>A supercell of (2x2x2) has to contain 2*2*2=8 times the
number of atoms of the unit cell. So It can never have an
odd number as in your case 63. You should follow a
tutorial on how to prepare such a structure, e.g. with
ASE. Here, for example, you find instruction on how to
build a crystal: <a
href="http://exciting-code.org/lithium-atomic-simulation-environment"
target="_blank" moz-do-not-send="true">http://exciting-code.org/lithium-atomic-simulation-environment</a>.
Once you have the ASE Atoms object building the supercell
is as easy as atoms*(2,2,2). When you have a correct
crystal, make sure that the &CELL section in the cp2k
input matches the lattice dimensions of the crystal. You
cannot just use an arbitrary number.</p>
<p>CELL_OPT will optimize both the atom positions as well as
the lattice dimensions.</p>
<p>Fabian<br>
</p>
<div>On 12.05.2021 06:19, sumit agrawal wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr"><br>
Dear Lucas Lodeiro and Fabian,<br>
<div><br>
</div>
<div>Thanks for your nice suggestions. I am new to cp2k.
I have just started learning this. I have some
query regarding my procedure for preparation for
crystal structure. I am following below procedure to
prepare the crystal structure:</div>
<div><br>
</div>
<div>First, I have prepared the crystal structure
(2x2x2) with the lattice dimension a=5.2229 A,
b=5.2229 A and c=5.2229 A. It contains 63 atoms. After
that I removed some atoms from x, y and z directions
so that it become periodic in x, y and z direction.
After this, it contains 32 atoms. </div>
<div>Now I save this lattice in XYZ format. This will be
my initial coordinate system. Am I correct?</div>
<div><br>
</div>
<div>After this I took this coordinate file and ran for
the cp2k calculation.</div>
<div><br>
</div>
<div>Now in cp2k calculations for this lattice structure
what will be my cube size? (Here you mention it will
not be 20 A. )</div>
<div><br>
</div>
<div>One more query, here I am starting with a lattice
dimension with 5.2229 A . So after Cell_OPTIMIZATION,
will the geometry of my crystal change or not?</div>
<div><br>
</div>
<div>Yes, dispersion correction must be required for
this type of calculation, I will do that.</div>
<div><br>
</div>
<div>Here I am attaching my crystal structure images.</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>Thanks </div>
<div>Sumit</div>
<div><br>
</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, May 11, 2021
at 11:02 PM Lucas Lodeiro <<a
href="mailto:eluni...@gmail.com" target="_blank"
moz-do-not-send="true">eluni...@gmail.com</a>>
wrote:<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">Hi Sumit,
<div><br>
</div>
<div>First of all, you cannot find the lattice
constant with this type of calculation. You ran an
ENERGY calculation. If you want to do it, you need
to run a CELL_OPT calculation.</div>
<div>In your current calculation, you use a 20 A
lattice constant cube. Also, I think your initial
cell dimension is not correct, since the lattice
constant of Argon is 5.26 A, then a 2x2x2
supercell is not 20 A sized. Also, your system has
63 atoms... ¿?.</div>
<div><br>
</div>
<div>Other related topics are: a 2x2x2 supercell is
not sufficient to compute a periodical Argon
system... You need a bigger supercell, or use
kpoints. Also, as this system just interacts by
dispersion, probably the PBE functional is not
sufficient at all. You need to account the
dispersion terms by means of Grimes D3 or other.</div>
<div><br>
</div>
<div>Regards</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">El mar, 11 may
2021 a las 14:08, sumit agrawal (<<a
href="mailto:sumitag...@gmail.com"
target="_blank" moz-do-not-send="true">sumitag...@gmail.com</a>>)
escribió:<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">Hii everyone,<br>
<div><br>
</div>
<div>I want to calculate a lattice constant for
the Ar crystal of (2*2*2 unit cell). I am
attaching my input and out files. Where I will
find the lattice constant ?</div>
<div><br>
</div>
<div>Please help me!!</div>
<div><br>
</div>
<div><br>
</div>
</div>
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