  Using density functionals from fundamental measure theory, phase diagrams and
crystal-fluid surface tensions in additive and nonadditive (Asakura-Oosawa
model) two-dimensional hard disk mixtures are determined for the whole range of
size ratios $q$ between disks, assuming random disorder in the crystal phase.
The fluid-crystal transitions are first-order due to the assumption of a
periodic unit cell in the density functional calculations. Qualitatively, the
shape of the phase diagrams is similar to the case of three-dimensional hard
sphere mixtures. For the nonadditive case, a broadening of the fluid-crystal
coexistence region is found for small $q$ whereas for higher $q$ a vapor--fluid
transition intervenes. In the additive case, we find a sequence of spindle
type, azeotropic and eutectic phase diagrams upon lowering $q$ from 1 to 0.6.
The transition from azeotropic to eutectic is different from the
three-dimensional case. Surface tensions in general become smaller (up to a
factor 2) upon addition of a second species and they are rather small. The
minimization of the functionals proceeds without restrictions and optimized
graphics card routines are used.
