We introduce a real-space approach to understand the relationship between optical absorption and crystal structure. We apply this approach to alternative phases of silicon, with a focus on the Si20 crystal phase as a case study. We find that about 83% of the changes in the calculated low-energy absorption in Si20 as compared to Si in the diamond structure can be attributed to reducing the differences between the on-site energies of the bonding and anti-bonding orbitals as well as increasing the hopping integrals for specific Si-Si bonds.
@article{arxiv.1706.07382,
title = {Real-space study of the optical absorption in alternative phases of silicon},
author = {Chin Shen Ong and Sinisa Coh and Marvin L. Cohen and Steven G. Louie},
journal= {arXiv preprint arXiv:1706.07382},
year = {2018}
}