  Accretion disks formed in binary neutron star mergers play a central role in
many astrophysical processes of interest, including the launching of
relativistic jets or the ejection of neutron-rich matter hosting heavy element
nucleosynthesis. In this work we analyze in detail the properties of accretion
disks from 44 ab initio binary neutron star merger simulations for a large set
of nuclear equations of state, binary mass ratios and remnant fates, with the
aim of furnishing reliable initial conditions for disk simulations and a
comprehensive characterization of their properties. We find that the disks have
a significant thermal support, with an aspect ratio decreasing with the mass
ratio of the binary from $\sim 0.7$ to 0.3. Even if the disk sample spans a
broad range in mass and angular momentum, their ratio is independent from the
equation of state and from the mass ratio. This can be traced back to the
rotational profile of the disc, characterized by a constant specific angular
momentum (as opposed to a Keplerian one) of $3-5 \times 10^{16} \rm ~
cm^2~s^{-1}$. The profiles of the entropy per baryon and of the electron
fraction depend on the mass ratio of the binary. For more symmetric binaries,
they follow a sigmoidal distribution as a function of the rest mass density,
for which we provide a detailed description and a fit. The disk properties
discussed in this work can be used as a robust set of initial conditions for
future long-term simulations of accretion disks from binary neutron star
mergers, posing the basis for a progress in the quantitative study of the
outflow properties.
