  First-principles calculations have become a powerful tool to exclude the
Edisonian approach in search of novel 2d materials. However, no universal
first-principles criteria to examine the realizability of hypothetical 2d
materials have been established in the literature yet. Because of this, and
since the calculations are always performed in an artificial simulation
environment, one can unintentionally study compounds that do not exist in the
experiments. Although investigations of physics and chemistry of unrealizable
materials can provide some fundamental knowledge, the discussion of their
applications can mislead experimentalists for years and increase the gap
between experimental and theoretical research. By analyzing energy convex hull,
phonon spectra, and structure evolution during ab initio molecular dynamics
simulations for a range of synthesized and recently proposed 2d materials, we
construct energy, phonon, and dynamic stability filters which need to be
satisfied before proposing novel 2d compounds. We demonstrate the power of the
suggested filters for several selected 2d systems, revealing that some of them
cannot be ever realized experimentally.
