[Wien] doped question

[genghua]

>Dear sir,
>     I`m happy tell you that everything is ok when I use yushan give me .struct,
>thank you very much for your kind help,I have another question to bother you ,
>since I am very unfamilar with anatase,and have never done doped anatase,when
> I construct supercell,there are following :
>Number of cells in x direction: 
>2
> Number of cells in y direction: 
>2
> Number of cells in z direction: 
>2
> 
> Current structure has lattice type P   
> Enter your target lattice type: (P,B,F)
>p
> Target lattice type will be P 
>is it right?  
>  and following information 
> "Add vacuum in x-direction for surface-slab [bohr]:"I don`t unsderstand what`s mean.
>could you give me some suggestion?
>  after construct supercell,how to dop B in it ?just replace oxygen by B ? and is it necessory to  optimize struct ? 
>      
>			 
>　　　　　　　　genghua
>　　　　　　　　hgeng at iccas.ac.cn
>　　　　　　　　　　2004-02-07