  We have investigated the structural, elastic, electronic, thermophysical,
superconducting, and optical properties of ScYH6 under uniform hydrostatic
pressures up to 25 GPa, using the density functional theory (DFT) formalism.
Most of results reported here are novel. The compound ScYH6 has been found to
be elastically and thermodynamically stable within the pressure range
considered. The compound is brittle; the brittleness decreases with increasing
pressure. The elastic anisotropy is low and the machinability index is moderate
which increases gradually with rising pressure. The compound is a hard
material. The electronic band structure shows weakly metallic character with
low density of states at the Fermi level. The Debye temperature of the compound
is high and increases with increasing pressure. The Gr\"uneisen parameter of
ScYH6 is low and the phonon thermal conductivity is high at room temperature.
The compound is a very efficient reflector of infrared radiation. The compound
is also an efficient absorber of visible and ultraviolet light. The overall
effect of pressure on optical parameters is small. We have also investigated
the pressure induced changes in the predicted superconducting state properties
by considering the changes in the electronic density of states at the Fermi
level, Debye temperature, and the repulsive Coulomb pseudopotential. The
superconducting transition temperature is found to increase gradually with
increasing pressure.
