  We studied by molecular dynamics simulations the relation existing between
the lifetime of hydrogen bonds, the tetrahedral order and the diffusion
coefficient of model water. We tested four different models: SPC/E, TIP4P-Ew,
TIP5P-Ew and Six-site, these last two having sites explicitly resembling the
water lone pairs. While all the models perform reasonably well at ambient
conditions, their behavior is significantly different for temperatures below
270 K. The models with explicit lone-pairs have a longer hydrogen bond
lifetime, a better tetrahedral order and a smaller diffusion coefficient than
the models without them.
