[CP2K:7809] Cell optimization : z direction constraint

[ashish dabral]

Thanks for your input S Ling. I have a lot of servers with cp2k compiled 
for them. It is not reasonable to do it again just to control the z height 
as a lot of other people use the same 
code. If recompilation is the only way then I would rather go for an 
increased vacuum.

Thanks

On Friday, 27 May 2016 18:31:10 UTC+2, S Ling wrote:
>
> Hi
>
> 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 
> details.
>
> 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.
>
> SL
>
>
>
> On 27 May 2016 at 16:54, ashish dabral <ashis... at gmail.com <javascript:>
> > 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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