I would like to recommend that USPEX support Copy OPTCELL file into CalcFold1-CalcFoldN directory

[Jack]

Here, When I try to use the 2D materials function in USPEX, the OPTCELL file is very efficient to optimize these 2D structures in  CalcFold1-CalcFoldN directory.

So I recommend that USPEX support Copy OPTCELL file into CalcFold1-CalcFoldN directory. 

For example, When the User put the OPTCELL file in the Specific directory, the USPEX could automatically copy this file into CalcFold1-CalcFoldN directory.  Sadly, Now the USPEX does not support this function, and I have to artificially copy the OPTCELL file into CalcFold1-CalcFoldN directory. 

The OPTCELL file is like, which could be useful and helpful to optimize 2D structures after I edit the constr_cell_relax.F in vasp.

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