Pressure-induced structural phase transformation of yttrium diborocarbide at high pressure

Abstract

Using an efficient structure search method combined with first-principles calculations, the structural behavior of YB2C2 has been extensively investigated in a wide pressure range of 0–200 GPa. A structural phase transition from the ambient tetragonal phase to a new high-pressure tetragonal phase was uncovered above 110 GPa. By total-energy calculations, this pressure-induced structural phase transition was determined to be first order with a volume drop of 9.1%. Inspections of crystal and electronic structures indicated that this high-pressure phase exhibits a 3D sp3 B-C network built up from the sharply distortions and reconstructions of the 2D B-C layers in the ambient-pressure phase under compression, leading to an improved mechanical ductility and weakened elastic anisotropy.