  We introduce QM7-X, a comprehensive dataset of 42 physicochemical properties
for $\approx$ 4.2 M equilibrium and non-equilibrium structures of small organic
molecules with up to seven non-hydrogen (C, N, O, S, Cl) atoms. To span this
fundamentally important region of chemical compound space (CCS), QM7-X includes
an exhaustive sampling of (meta-)stable equilibrium structures - comprised of
constitutional/structural isomers and stereoisomers, e.g., enantiomers and
diastereomers (including cis-/trans- and conformational isomers) - as well as
100 non-equilibrium structural variations thereof to reach a total of $\approx$
4.2 M molecular structures. Computed at the tightly converged
quantum-mechanical PBE0+MBD level of theory, QM7-X contains global (molecular)
and local (atom-in-a-molecule) properties ranging from ground state quantities
(such as atomization energies and dipole moments) to response quantities (such
as polarizability tensors and dispersion coefficients). By providing a
systematic, extensive, and tightly-converged dataset of quantum-mechanically
computed physicochemical properties, we expect that QM7-X will play a critical
role in the development of next-generation machine-learning based models for
exploring greater swaths of CCS and performing in silico design of molecules
with targeted properties.
