The interband optical conductivity tensor, sigma 1, of the ceramic oxide La2CuO4 has been calculated using the linear muffin-tin orbital method. The calculation shows that the optical conductivity is strongly anisotropic, and that this is due to the quasi two dimensional nature of the electronic structure in this material. A relatively strong peak at 1 eV appears in the a-b components of sigma 1( omega ), which the authors compare with available experimental results. From their results they deduce a plasmon energy of 2.3 eV which is close to the values used to fit the experimental reflectivity using the Drude model.
 

Physica C, 153-155 1233-4, 1988.