  Motivated by contradicting reports in the literature, we have investigated
the structural stability of tungsten nanoparticles using density functional
theory calculations. The comparison of BCC, FCC, A15, disordered, and
icosahedral configurations unequivocally shows that BCC is the energetically
most stable structure when the number of atoms is greater than 40. A disordered
structure is more stable for smaller sizes. This result conflicts with an
earlier theoretical study on transition metal nanoparticles, based on a
semi-empirical modeling of nanoparticles energetics [D. Tom{\'a}nek et al.,
Phys. Rev. B \textbf{28}, 665 (1983)]. Examining this latter work in the light
of our results suggests that an erroneous description of clusters geometry is
the source of the discrepancy. Finally, we improve the accuracy of the
semi-empirical model proposed in this work, which will be useful to calculate
nanoparticle energies for larger sizes.
