Optical properties of metal-organic networks from distributed atomic polarizabilities

Metal-organic networks have become very popular materials in view of various chemical and physico-chemical applications. Much attention is normally focused on porous compounds (metal-organic frameworks), although densely packed polymers may also find applications. In this paper, we propose a rather simplified method to estimate the dielectric constants and the optical indicatrices of metal-organic networks, which could be useful for rapid selection of materials with specific optical properties. The method adopts the distributed atomic polarizabilities calculated for secondary building units of metal-organic networks. With the atomic quantities, one can evaluate the crystal susceptibility, assuming an oriented gas model corrected for the polarization induced by the crystal medium. A simple oriented gas model enables a rapid evaluation of the anisotropy of the optical indicatrix of a crystal, as confirmed by calculations under periodic boundary conditions. The correction for polarization induced by the crystalline environment provides, in addition, more accurate estimation of the refractive indices, at least in the regime of low frequencies. The computational costs are smaller than those for fully periodic calculations and could be significantly smaller if a set of precomputed, transferable atomic polarizabilities would be used.