  The presence of lone pair (LP) electrons is strongly associated with the
disruption of lattice heat transport, which is a critical component of
strategies to achieve efficient thermoelectric energy conversion. By exploiting
an empirical relationship between lattice thermal conductivity $\kappa_L$ and
the bond angles of pnictogen group LP cation coordination environments, we
develop an inverse design strategy based on a materials database screening to
identify chalcogenide materials with ultralow $\kappa_L$ for thermoelectrics.
Screening the $\sim$ 635,000 real and hypothetical inorganic crystals of the
Open Quantum Materials Database based on the constituent elements, nominal
electron counting, LP cation coordination environment, and synthesizability, we
identify 189 compounds expected to exhibit ultralow $\kappa_L$. As a
validation, we explicitly compute the lattice dynamical properties of two of
the compounds (Cu$_2$AgBiPbS$_4$ and MnTl$_2$As$_2$S$_5$) using
first-principles calculations and successfully find both achieve ultralow
$\kappa_L$ values at room temperature of $\sim$ 0.3--0.4 W/(m$\cdot$K)
corresponding to the amorphous limit. Our data-driven approach provides
promising candidates for thermoelectric materials and opens new avenues for the
design of phononic properties of materials.
