Token SIGMA= of cast double (optional)

Screening core radii used to make 's if the token IALPHA=0. They are read as follows:

STR ATOM=i SIGMA=si(0,i) ... si(lmx,i)
    ATOM=j SIGMA=si(0,j) ... si(lmx,j)
    ...

Where the si's are numbers, one for each and atom.