# Optical properties of lowest-energy carbon allotropes from the first-principles calculations

## TL;DR

This study employs first-principles calculations to analyze and predict the optical properties of the lowest-energy carbon allotropes, including their dielectric functions and Raman spectra across infrared, visible, and ultraviolet ranges.

## Contribution

It provides new theoretical predictions of optical constants and spectra for hypothetical carbon allotropes and lonsdaleite, expanding understanding beyond known diamond properties.

## Key findings

- Accurately modeled optical properties of cubic diamond
- Predicted optical constants for hypothetical allotropes and lonsdaleite
- Calculated Raman spectra across multiple light ranges

## Abstract

We study the optical properties of lowest-energy carbon allotropes in the infrared, visible and ultra-violet ranges of light in the general gradient approximation of the density functional theory. In our calculations we used the all-electron approach as well as the pseudo-potential approximation. In the infrared range, the complex dielectric functions, infrared and Raman spectra have been calculated using CRYSTAL14 program. The electronic properties and energy-dependent dielectric functions in the visible and ultraviolet ranges have been calculated using VASP program. We have described with a good accuracy experimentally known optical properties of cubic diamond crystal. Using obtained set of relevant parameters for calculations, we have predicted optical constants, dielectric functions and Raman spectra for the lowest-energy hypothetical carbon allotropes and lonsdaleite.