Structural stability and mechanism of compression of stoichiometric B13C2 up to 68 GPa

TL;DR

This study investigates the compression behavior of stoichiometric B13C2 boron carbide up to 68 GPa, revealing structural stability and clarifying its bonding mechanisms without phase transitions.

Contribution

It provides the first detailed analysis of B13C2's behavior under high pressure, resolving a long-standing scientific dispute about its compression mechanism.

Findings

B13C2 maintains its crystal structure up to 68 GPa

Unit cell and B12 icosahedra volumes decrease similarly under pressure

No molecular-like behavior observed during compression

Abstract

Boron carbide is a ceramic material with unique properties widely used in numerous, including armor, applications. Its mechanical properties, mechanism of compression, and limits of stability are of both scientific and practical value. Here, we report the behavior of the stoichiometric boron carbide B13C2 studied on single crystals up to 68 GPa. As revealed by synchrotron X-ray diffraction, B13C2 maintains its crystal structure and does not undergo phase transitions. Accurate measurements of the unit cell and B12 icosahedra volumes as a function of pressure led to conclusion that they reduce similarly upon compression that is typical for covalently bonded solids. A comparison of the compressional behavior of B13C2 with that of alpha-B, gamma-B, and B4C showed that it is determined by the types of bonding involved in the course of compression. Neither molecular-like nor inversed-molecular-like solid behavior upon compression was detected that closes a long-standing scientific dispute.