[CP2K:10592] Clarification on cell size and range

hut... at chem.uzh.ch hut... at chem.uzh.ch
Thu Aug 2 07:07:08 UTC 2018


the size of the cell is in your case 10.8649^3 as defined in the input.
Because there is translational invariance, the position of the cell
is not defined. Internally, CP2K works with a computational cell
defined by

x = x - A * NINT(x/A)

Some calculations are done in other cells, e.g. the plane wave

Atomic positions during MD/Geometry optimization are not folded
back for output (only internally for the force calculation).


Juerg Hutter
Juerg Hutter                         Phone : ++41 44 635 4491
Institut für Chemie C                FAX   : ++41 44 635 6838
Universität Zürich                   E-mail: hut... at chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland

-----cp... at googlegroups.com wrote: -----
To: "cp2k" <cp... at googlegroups.com>
From: gaston.... at gmail.com
Sent by: cp... at googlegroups.com
Date: 08/01/2018 03:27PM
Subject: [CP2K:10592] Clarification on cell size and range

Hi everybody,

I am new to CP2K and I atrying to understand a few things about the cell :
What is the size of the cell and it's range?

With the following part of the input file (more attached)

      A     10.86490000    0.000000000    0.000000000
      B     0.000000000    10.86490000    0.000000000
      C     0.000000000    0.000000000    10.86490000

I get negative positions in [-10.86490000 ; +10.86490000]  while running an MD simulation with positive initial positions.
Does that mean that the cell ranges from   -10.86490000 to +10.86490000??

On the other hand in the output file I get the following message :
 CELL_TOP| Volume [angstrom^3]:                                         1282.559
 CELL_TOP| Vector a [angstrom    10.865     0.000     0.000    |a| =      10.865
 CELL_TOP| Vector b [angstrom     0.000    10.865     0.000    |b| =      10.865
 CELL_TOP| Vector c [angstrom     0.000     0.000    10.865    |c| =      10.865

The volume here is  1282.559 = 10.865^3 
This seems to indicate that the cell ranges from 0 to +10.8650000!!

Can anyone clarify this point please?

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[attachment "run.inp" removed by Jürg Hutter/at/UZH]

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