How to calculate refractive index and extinction coefficient


How do we calculate the refractive index and extinction coefficient of a material over a range of wavelengths?


I will give you some suggestions based on my understanding of the dielectric function, hoping to help you.
First of all, you need to learn how to calculate the real and imaginary parts of the dielectric function, which is related to the tutorial Optic - abinit. Then you need to judge the number of independent tensors of the dielectric function according to the symmetry of the system you are studying. For details, please refer to and
Then you can calculate textinction coefficient k(ω), absorption coefficient α(ω), refractive index n(ω), energy-loss spectrum L(ω) and reflectivity R(ω) according to the relevant formula in this document Ab initio study of the linear and nonlinear optical responses in BiAlO3: Philosophical Magazine: Vol 96, No 2 ( I hope my answer can help you, if there is anything wrong, please correct me.