  A comparative density functional plus dynamical mean field theory study of
the pseudocubic ruthenate materials CaRuO$_3$ and SrRuO$_3$ is presented. Phase
diagrams are determined for both materials as a function of Hubbard repulsion
$U$ and Hund's rule coupling $J$. Metallic and insulating phases are found, as
are ferromagnetic and paramagnetic states. The locations of the relevant phase
boundaries are determined. Based on the computed phase diagrams, Mott-dominated
and Hund's dominated regimes of strong correlation are distinguished.
Comparison of calculated properties to experiments indicates that the actual
materials are in the Hund's coupling dominated region of the phase diagram so
can be characterized as Hund's metals, in common with other members of the
ruthenate family. Comparison of the phase diagrams for the two materials
reveals the role played by rotational and tilt (GdFeO$_3$-type) distortions of
the ideal perovskite structure. The presence of magnetism in SrRuO$_3$ and its
absence in CaRuO$_3$ despite the larger mass and larger tilt/rotational
distortion amplitude of CaRuO$_3$ can be understood in terms of density of
states effects in the presence of strong Hund's coupling. Comparison of the
calculated low-$T$ properties of CaRuO$_3$ to those of SrRuO$_3$ provides
insight into the effects of magnetic order on the properties of a Hund's metal.
The study provides a simultaneous description of magnetism and correlations and
explicates the roles played by band theory and Hubbard and Hund's interactions.
