A theoretical study of pressure-induced phase transitions and electronic band structure of anti-A-sesquioxide type γ-Be3N2

Structural parameters and electronic band structure of anti-A-sesquioxide (aAs) type gamma-Be3N2 are presented following the first-principles linear combination of atomic orbitals method within the framework of a posteriori density-functional theory implemented in the CRYSTAL code. Pressure-induced phase transitions among the four polymorphs alpha, beta, cubic-gamma and aAs-gamma of Be3N2 are examined. Enthalpy-pressure curves do not show the possibility of pressure-induced structural phase transition to the cubic-gamma phase. However, alpha -> aAs-gamma and beta -> aAs-gamma structural phase transitions are observed at 139 GPa and 93 GPa, respectively. Band structure calculations predict that aAs-gamma Be3N2 is an indirect semiconductor with 4.73 eV bandgap at L point. Variation of bandgap with pressure and deformation potentials are studied for the alpha, beta and aAs-gamma polymorphs. Pressure-dependent band structure calculations reveal that, within the low-pressure limit, bandgaps of beta and aAs-gamma increase with pressure unlike alpha-Be3N2.