Possible complete miscibility of $(BN)_x(C_2)_{1-x}$ alloys

TL;DR

This study uses ab initio calculations to explore the stability and phase diagram of $(BN)_x(C_2)_{1-x}$ alloys, revealing they can be completely miscible, contrary to earlier predictions but aligning with experimental data.

Contribution

The paper demonstrates the potential for complete miscibility in $(BN)_x(C_2)_{1-x}$ alloys through detailed ab initio analysis and phase diagram construction.

Findings

$(BN)_1/(C_2)_1$ superlattices have lowest formation energy in (111) orientation.

Complete miscibility of $(BN)_x(C_2)_{1-x}$ alloys is possible.

Results agree with experimental reports, contradicting previous theories.

Abstract

The stabilities of $(BN)_x(C_2)_{1-x}$ alloys and related superlattices are investigated by ab initio pseudopotential calculations. We find that the $(BN)_1/(C_2)_1$ superlattices in (111) orientations have the lowest formation energy among many short-range ordered $BNC_2$ structures due to the smallest number of B-C and C-N bonds. Based on the calculated formation energies at several compositions and for various ordered structures and assuming thermodynamic equilibrium, the solid solution phase diagram of $(BN)_x(C_2)_{1-x}$ alloys is constructed. We find that the complete miscibility of $(BN)_x(C_2)_{1-x}$ alloys is possible, which is in contrast with previous theoretical predictions but in agreement with experimental reports.