First-Principles Study of Optical Properties of Linde-Type A Zeolite

Within the framework of density functional theory, electronic structures of Linde-type A (LTA) zeolite membranes are calculated, and based on the electronic structures, several key optical properties of LTA zeolite membranes can be conveniently determined, with the method of the full-potential linearized augmented plane wave under the random phase approximation for the boundaries and the generalized gradient approximation for the exchange-correlation potentials. The calculated optical properties as a function of frequency include the real and imaginary parts of the dielectric function epsilon(omega), the refraction index n(omega), the extinction coefficient k(omega), the reflectivity R(omega), the energy loss function L(omega), the absorption coefficient alpha(omega), and finally the optical conductivity sigma(omega), along with specific directions of the primitive cell. It is demonstrated that the optical properties of the sodium LTA zeolite cluster appear anisotropic within the range of UV. The nature of anisotropy implies that all the functions are 3 x 3 tensors with nonzero off-diagonal elements. Three diagonal and three off-diagonal elements are simultaneously presented.