Amorphous silicon hexaboride at high pressure

ABSTRACT

We investigate the pressure-induced structural phase transformation of amorphous silicon hexaboride (a-SiB₆) using a constant pressure first principles approach. a-SiB₆ is found to undergo a gradual phase transformation to a high-density amorphous phase (HDA) in which the average coordination number of both B and Si atoms is about 6. The HDA phase consists of differently coordinated motifs ranging from 4 to 8. B₁₂ icosahedra are found to persist during compression of a-SiB₆ and the structural modifications primarily occur around Si atoms and in the regions linking pentagonal pyramid-like configurations to each other. Upon pressure release, an amorphous structure, similar to the uncompressed one, is recovered, indicating a reversible amorphous-to-amorphous phase change in a-SiB_6. When the electronic structure is considered, the HDA phase is perceived to have a wider forbidden band gap than the uncompressed one.

KEYWORDS:

• Amorphous solids
• phase transformations
• semiconducting ceramics
• ab initio

Acknowledgements

This work was supported by the Scientific and Technological Research Council of Turkey (TÜBİTAK) under grant number 117M372. The simulations were run on the TÜBİTAK ULAKBİM, High Performance and Grid Computing Center (TRUBA resources).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Scientific and Technological Research Council of Turkey (TÜBİTAK) [grant number 117M372].