[CP2K-user] [CP2K:11539] Lattice Constant Optimization

[hut... at chem.uzh.ch]

Hi

the problem is related to your use of 
    &CELL
      ABC 3.60 3.60 3.60
      PERIODIC XYZ
      MULTIPLE_UNIT_CELL 2 2 2   <<<<<<<<<<<<<<<<<<<<<
    &END CELL
This requests a doubling of the cell in all directions.
However, if you also want to multiply the atoms you need
    &TOPOLOGY
      MULTIPLE_UNIT_CELL 2 2 2
    &END
in the &SUBSYS section. With your setting you had 8 atoms in a 
cell for 64 atoms.

BTW you are using k-points, why do you want to also use multiple
    unit cells?

regards

Juerg

--------------------------------------------------------------
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: "Brian Day" <22b... at gmail.com>
Sent by: cp... at googlegroups.com
Date: 04/04/2019 07:25PM
Subject: [CP2K:11539] Lattice Constant Optimization

As practice with crystalline materials, I was trying to determine the lattice constant of FCC Cu in CP2K. My approach was to vary the lattice constant, perform an energy calculation, and ultimately plot the energy vs. lattice constant to determine the minimum. However, when I did this the energy simply decreased as the lattice constant increased, without any minimum. I tried this both with and without D3. 

Here is an overview of my results. The first value is the lattice constant in angstrom, and the second is the energy in Hartree. 
             Cu - PBE                  Cu - PBE - D3 
 3.45      -382.08717                -382.08717 
 3.50      -382.32915                -382.32915 
 3.55      -382.54857                -382.54857 
 3.60      -382.74734                -382.74734 
 3.65      -382.92688                -382.92688 
 3.70      -383.08999                -383.08999 
 3.75      -383.23701                -383.23701 
 3.80      -383.37008                -383.37008 

I have also attached a sample input file. If anybody could offer some insight as to why I am seeing this behavior that would be greatly appreciated. 

Best,
     Brian  
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[attachment "Cu_3.60-run.inp" removed by Jürg Hutter/at/UZH]