Soft-Square Function

For POTential=SOFTsquare, the square-well function is used for distances within a specified ``switching" region ($r_{sw}$, specified by the RSWITch statement), whereas outside this region a ``soft" asymptote is used:

$$E_{NOE}^{class}= {\rm min}(ceil,S C) \left\{ \begin{array}... ...\mbox{$R < d+d_{plus}-d_{off} + r_{sw}$} \end{array} \right.$$

where $\Delta$ is given by Eq. 20.11 and $a$ and $b$ are determined by the program such that $E_{NOE}^{class}$ is a smooth function at the point $R=d+d_{plus}-d_{off} + r_{sw}$. The slope of the asymptote $c$ is specified by the ASYMptote statement, $r_{sw}$ is specified by the RSWItch statement, and the exponent $softexp$ is specified by the SOEXponent statement. The distance $R$ is defined in Section 20.2.