Pseudopotential for Ge

This problem explores the suitability of

$$V_{ps}(r)=-\frac{Z_v}{r} \frac{1-e^{-\lambda r}}{1+e^{-\lambda(r-r_c)}},$$ (1)

as a pseudopotential for germanium (Ge) when $Z_v \equiv 4$, $r_c\equiv 1.052$ bohr, and $\lambda\equiv 18.5$ bohr$^{-1}$. This will not involve much development of new code but mostly quickly modifying (``hacking'') your atomic solver in ``broyden.c''