Title: Structure, Stability, and Electronic Properties of Boron Suboxide: A Density Functional Theory Study

Abstract

Boron suboxide (B₆O) is a boron-rich compound derived from the α-rhombohedral boron lattice with extreme hardness and unusual semiconducting properties. In this work, density functional theory (DFT) was used to show that unit cell volume, mechanical strength, band gaps, and thermodynamic stabilities of B₆O were influenced by the interstitial elements and point defects at the icosahedral sites. While the hexagonal unit cell volume (HUCV) varies with interstitial occupancy, it is the icosahedral defect that weakens the intrinsic bulk modulus of B₆O. Using the hybrid HSE functional, we confirmed that the perfect B₆O bulk is a p-type semiconductor with a direct band gap of 2.8 eV. Furthermore, by screening α-boron compounds systematically, we found that a simple octet rule may offer a consistent explanation for the variations in the computed electronic structures. The formation free energies calculated over a wide range of temperatures (0–2500 K) and pressures (0–80 GPa) predict that formations of interstitial defects become favorable only at higher temperatures (ca. 1800 K) in bulk B₆O lattices. The nudged elastic band (NEB) method was employed to identify the minimum energy pathways for the diffusions of dislocated B and O atoms. The diffusion of icosahedral B atoms has an energy barriermore » of 0.16 eV. More complex B diffusion paths involving the reorganization of icosahedral boron atoms incur higher barriers (>1 eV). In contrast, the diffusion of interstitial O atoms is facile with a barrier of 0.4 eV. Lastly, successive O insertions into the α-B lattice were performed using DFT to generate a basic understanding of the oxidation process. Furthermore, these calculations provide fundamental atomistic insights into the growth of B₆O crystals and control of their point defects.« less

Authors:

Liu, Bin  ^[1];

• Search DOE PAGES for author "Liu, Bin"
• Search DOE PAGES for ORCID "0000-0001-7890-7612"

Evans, Dylan ^[1]; Deng, Hao  ^[1];

• Search DOE PAGES for author "Deng, Hao"
• Search DOE PAGES for ORCID "0000-0002-1656-229X"

Edgar, James ^[1]

---

+ Show Author Affiliations

1. Kansas State Univ., Manhattan, KS (United States)

Publication Date:

Tue Sep 13 00:00:00 EDT 2022

Research Org.:

Kansas State Univ., Manhattan, KS (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)

OSTI Identifier:

1894427

Grant/Contract Number:  

SC0021264; AC02-05CH11231; CHE-1726332; CNS-1006860; EPS-1006860; EPS-0919443

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Physical Chemistry. C

Additional Journal Information:

Journal Volume: 126; Journal Issue: 37; Journal ID: ISSN 1932-7447

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Chemical structure; Defects; Energy; Lattices; Potential energy