[CP2K:7809] Cell optimization : z direction constraint

S Ling lingsa... at gmail.com
Fri May 27 16:31:08 UTC 2016


If you have vacuum in your model, and you want to keep z fixed during
cell_opt, then you need to modify the code and recompile it, see
https://groups.google.com/d/msg/cp2k/XescBifa_ik/SHSnf1G5QdgJ for more

Basically, you need to go to your CP2K source code, find the
cell_opt_utils.F file (located in $CP2K/cp2k/src/motion directory), go to
the end of the file and add "gradient(6) = 0.0_dp" below "gradient =
-gradient". Then you will need to recompile the code and run your
calculation with the new executable.


On 27 May 2016 at 16:54, ashish dabral <ashishd... at gmail.com> wrote:

> Hi,
> Can someone explain to me how I can do a Cell optimization with a fixed z
> direction(height) while everything else (including atomic coordinates)
> can change? I usually take 20A as the z height (supercell z vector length)
> for my 2d systems to isolate image cell interactions but apparently
> some structures are contracting in the z direction and reaching bulk state
> after 200 iterations, which is really time consuming. I want the system
> to move to prevent any stress but I do not want contraction because it
> does not remain 2d anymore.
> Also, If I fix the vertical height, will it be right? I mean if the
> original system with that vertical height want to contract then it has
> interactions
> with the image cell. If I fix the height then I would still have the
> interactions with the image cell above but will not see it in optimized
> structure.
> Will this be right approach?
> Thanks
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