  The frozen-phonon method, used to calculate electron-phonon coupling effects,
requires calculations of the investigated structure using atomic coordinates
displaced according to a certain phonon eigenmode. The process of "freezing-in"
the specific phonon can bring electronic eigenstates that are energetically
close in energy into an anticrossing. This electronic anticrossing effect is,
however, unrelated to the wanted electron-phonon coupling, and needs to be
removed. We present a procedure how to deal with these problematic anticrossing
situations and apply it to the band gap zero-point motion renormalization of
sixteen diamondoids and urotropine using different exchange correlation
functionals. We find gap renormalizations of diamondoids in the range of 150 -
400 meV and only 62 meV for urotropine due to the lone-pair character of the
highest occupied molecular orbital of the latter.
