  In this article we present a caracterization of the vibrational spectrum of
the H5+ molecule using the correlation function quantum Monte Carlo (CFQMC)
method and a genetic algorithm study of the topology of the potential energy
surface used in this work. The vibrational modes associated with the H3+ - H2
torsion and stretching posses very flat minima. As a consequence the
fundamental frequencies corresponding to these modes are poorly described in
the harmonic approximation. The vibrational frequencies obtained in this work
are in good agreement with the available experimental data as well as other
computational methods found in literature. In our genetic algorithm study of
the potential energy surface using cartesian coordinates we have found some
unexpected minima. A careful analysis shows that some of these minima are
described by the same curviliniar coordinates in which the potential is
described. However, they represent nonequivalent molecular geometries.
