We perform first principles density functional pseudopotential calculation for the description of band structure ans optical responses a prototypical family of quasi-molecular layered solid of the type Al₃ where A = Sb, Bi and As. Our report on calculation of the anisotropic frequency-dependent optical properties and density of states of these compounds and find excellent agreement with the available experimental data. The optical properties show to main structures that can attributed to transitions between the np-orbitals of A3+ -cations and 5²2 5p⁵ orbitals of I- -anions.
