  Hybrid or organic plastic crystals have the potential as lead-free
alternatives to conventional inorganic ferroelectrics. These materials are
gaining attention for their multiaxial ferroelectricity, above-room-temperature
Curie temperatures, and low-temperature synthesis. Here, we report a screening
study of the Cambridge Structural Database (CSD) resulting in 55 new candidate
plastic and plastic ionic ferroelectric molecular crystals, along with 16
previously reported ferroelectrics. With over 1.2 million entries in the CSD,
the screening procedure involved many steps, including considerations of
molecular geometry and size, space group, and hydrogen bonding pattern. The
spontaneous polarization and electronic band gaps were predicted using density
functional theory. 21 of the candidate ferroelectrics have a polarization
greater than $10 \mathrm{{\mu}C/cm^2}$, out of which nine are reported at room
temperature.
