For POTential=SOFTsquare, the square-well function is used for distances within a specified ``switching" region (, specified by the RSWITch statement), whereas outside this region a ``soft" asymptote is used:
where is given by Eq. 18.9 and a and b are determined by the program such that is a smooth function at the point . The slope of the asymptote c is specified by the ASYMptote statement, is specified by the RSWItch statement, and the exponent softexp is specified by the SOEXponent statement. The distance R is defined in Section 18.2.