Ab initio calculations of optical properties of Li and K at high pressures

•In this work, we examined high pressure structural changes in Li and Potassium.•Optical properties are calculated.•We show that optical properties can be used to classify these elements into complex structures.

Detailed ab initio calculations of optical properties of Lithium and Potassium at high pressures over a wide range of frequencies are presented. We employ the Kramers–Kronig relation in the determination of the Infrared Spectra from the frequency dependent dielectric matrix. The Op8 Potassium structure which is an insulator, consists of complex superpositions of planes and structures. On the other hand, the fcc Potassium is opaque in the visible spectrum up to 16 eV and gradually turns transparent from 19.3 eV up to 21 eV. We showed that the optical properties of Potassium and Lithium can be used to explain the complex structures formed at high pressures by these elements.