(1) Insert a new line "if (iuserfunc==9999) userfunc=1/densellip(x,y,z,1)" to "function userfunc" part of function.f90
(2) Compile the source code
(3) Set "iuserfunc" in settings.ini to -9999
(4) Boot up Multiwfn and load your file, in the main function 2, select option -11, choose "100 User-defined real space function"
Then you can use various options to search critical points, generate topology paths and so on.
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