Density-functional theory methods and codes adopting periodic
boundary conditions are extensively used in condensed matter physics
and materials science research. In 2016, their precision (how well
properties computed with different codes agree among each other) was
systematically assessed on elemental crystals: a first crucial step to evaluate
the reliability of such computations. In this Expert Recommendation, we
discuss recommendations for verification studies aiming at further testing
precision and transferability of density-functional-theory computational
approaches and codes. We illustrate such recommendations using a greatly
expanded protocol covering the whole periodic table from Z = 1 to 96 and
characterizing 10 prototypical cubic compounds for each element: four
unaries and six oxides, spanning a wide range of coordination numbers
and oxidation states. The primary outcome is a reference dataset of
960 equations of state cross-checked between two all-electron codes,
then used to verify and improve nine pseudopotential-based approaches.
Finally, we discuss the extent to which the current results for total energies
can be reused for different goals.