  Using ab initio method we have studied the structural, elastic, electronic,
optical and thermodynamic properties of AlB2 and TaB2. We have used plane wave
pseudopotential with generalised gradient approximation as implemented in
CASTEP program. The independent elastic constants, bulk modulus, Young's
modulus, shear modulus, anisotropic factor, Pugh ratio, etc are calculated.
This results show that AlB2 and TaB2 are mechanically stable. We have also
calculated the band structure and density of states. Band structure results
show that AlB2 and TaB2 show metallic behaviour. In order to understand the
electronic properties in a better way we have also calculated dielectric
function, refractive index, absorption coefficient, conductivity, loss function
and reflectivity. Results of absorption coefficient and conductivity are in
good agreement with the band structure results. The effect of temperature and
pressure on the bulk modulus, Debye temperature, specific heat and also on the
thermal expansion coefficient are derived from the quasi-harmonic Debye model
with phononic effect in both cases.The results for the elastic and electronic
properties are compared to experimental measurements and with the results
obtained in different band-structure calculations, however, no optical data are
available for comparison.
