Using CASTEP I studied optical and electronic properties under increasing pressure effect. Observing absorption coefficient, reflectivity, conductivity, and band gap increase with increasing pressure. Now my question is that why so? Absorption and reflectivity have inversely linked but in my case not such. If considering the Tauc relation, the absorption coefficient and energy gap have a direct relation then the results of absorption are true but reflectivity should be reduced but not so. KIndly explain what is behind it?