  Direct bandgap bulk materials are very important for the optical
applications. It is therefore important to predict new materials with the
desired properties. In the present work, density functional theory is applied
to study different physical properties of X$_2$MgZ$_4$($X=$ Sc, Y; $Z=$ S, Se)
spinel compounds. Generalized gradient approximation is used to analyze the
structural and elastic parameters while modified Becke Johnson exchange
potential is applied to calculate electric band profiles and optical
properties. All the studied compounds are stable in the cubic structure. Also
the energy bandgap is of direct nature. Therefore these compounds can find
useful applications in the optoelectrics devices. Optical properties of the
compounds are studied in terms of dielectric function, refractive index,
extinction coefficient, optical conductivity and reflectivity. The transport
parameters like electrical conductivity, Seebeck coefficient, and thermal
conductivity are also evaluated.
