  The first-principles description of liquid water using ab initio molecular
dynamics (AIMD) based on Density Functional theory (DFT) has recently been
found to require long equilibration times, giving too low diffusivities and a
clear over-structuring of the liquid.
  In the light of these findings we compare here the room-temperature
description offered by two different exchange correlation functionals: BLYP,
the most popular for liquid water so far, and RPBE, a revision of the widely
used PBE.
  We find for RPBE a less structured liquid with radial distribution functions
closer to the experimental ones than the ones of BLYP.
  The diffusivity obtained with RPBE for heavy water is still 20% lower than
the corresponding experimental value, but it represents a substantial
improvement on the BLYP value, one order of magnitude lower than experiment.
  These characteristics and the hydrogen-bond (HB) network imperfection point
to an effective temperature ~3% lower than the actual simulation temperature
for the RPBE liquid, as compared with BLYP's ~17% deviation.
  The too long O--O average nearest-neighbor distance observed points to an
excessively weak HB, possibly compensating more fundamental errors in the DFT
description.
