Special usage: If you already have cube files of the two functions to be studied (referred to
as func1.cub and func2.cub, respectively) and you want to directly use the functions in postprocess
menu (e.g. plotting scatter map, modifying values), you should follow these steps: Input
the path of func1.cub after booting up Multiwfn, then enter main function 100 and select
subfunction 1, then input 0,0 when selecting real space functions, then input the path of func2.cub,
after that the grid data of the two cube files will be directly taken as function 1 and function 2.
Notice that, of course, the grid setting of func1.cub and func2.cub must be exactly identical.