  Many computational databases emerged over the last five years that report
material properties calculated with density functional theory. The properties
in these databases are commonly calculated to a precision that is set by choice
of the basis set and the k-point density for the Brillouin zone integration. We
determine how the precision of properties obtained from the Birch equation of
state for 29 transition metals and aluminum in the three common structures --
fcc, bcc, and hcp -- correlate with the k-point density and the precision of
the energy. We show that the precision of the equilibrium volume, bulk modulus,
and the pressure derivative of the bulk modulus correlate comparably well with
the k-point density and the precision of the energy, following an approximate
power law. We recommend the k-point density as the convergence parameter
because it is computationally efficient, easy to use as a direct input
parameter, and correlates with property precision at least as well as the
energy precision. We predict that common k-point density choices in high
throughput DFT databases result in precision for the volume of 0.1%, the bulk
modulus of 1%, and the pressure derivative of 10%.
