  Using the density functional theory (DFT) based first-principles
investigation, the structural, mechanical, hardness, elastic anisotropy,
optoelectronic, and thermal properties of cubic KB2H8 have been studied within
the uniform pressure range of 0 - 24 GPa. The calculated structural parameters
are in good agreement with the previous theoretical work. The compound KB2H8 is
found to be structurally and thermodynamically stable in the pressure range
from 8 GPa to 24 GPa. Single crystal elastic constants Cij and bulk elastic
moduli (B, G and Y) increase systematically with pressure from 8 GPa to 24 GPa.
In the stable phase, KB2H8 is moderately elastically anisotropic and ductile in
nature. The compound is highly machinable and fracture resistant. The Debye
temperature, melting temperature and thermal conductivity increases with
pressure. The results of electronic band structure calculations and optical
parameters at different pressures are consistent with each other. The compound
is optically isotropic. The compound KB2H8 has potential to be used as a very
efficient solar energy reflector. The electronic energy density of states at
the Fermi level decreases systematically with increasing pressure. The same
trend is found for the repulsive Coulomb pseudopotential. Possible relevance of
the studied properties to superconductivity has also been discussed in this
paper.
