  We have studied dilute Bose-Bose mixtures of atoms with attractive
interspecies and repulsive intraspecies interactions using quantum Monte Carlo
methods at $T=0$. Using a number of models for interactions, we determine the
range of validity of the universal equation of state of the symmetric liquid
mixture as a function of two parameters: the $s$-wave scattering length and the
effective range of the interaction potential. It is shown that the
Lee-Huang-Yang correction is sufficient only for extremely dilute liquids with
the additional restriction that the range of the potential is small enough.
Based on the quantum Monte Carlo equation of state we develop a new density
functional which goes beyond the Lee-Huang-Yang term and use it together with
local density approximation to determine density profiles of realistic
self-bound drops.
