[CP2K-user] Cell Optimization for Copper.

[Hasan Al-Mahayni]

Hello all,

I am fairly new to cp2k so I believe this issue is easily resolvable. My 
end goal is calculating adsorption energy of different molecules on copper 
surfaces (slab). However, the first step I need to do is optimize the cell 
parameters of copper(cell size). I know from materials project site that it 
is 3.62126 Angstroms. That is the configuration I start with and is 
attached by the name of "copper.xyz". The problem I am having is that when 
I run cell optimization on this (input file is "copper.inp"), I get the 
wrong results as the cell size shrinks (I get 3.4A). I think this is 
because of the vacuum between the copper cell and the simulation cell. My 
question is, what is the right way to set up the input file and especially 
the &CELL part. I started off by making the A B C cell size 10 A bigger 
than 3.62A, but that gives me the wrong result. If the A B C cell size is 
too small, I get an error saying geometry is wrong. Also, maybe GEO_OPT 
would be a more appropriate run type... I tried making supercell 2x2x2, 
3x3x3, and 4x4x4 while keeping ABC cell size 10 A bigger every time, and 
the result gets closer to 3.62 but this method is not ideal as the system 
gets bigger and bigger and the calculation is more computationally 
expensive. Any ideas?

Thanks,

Hasan.
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