Theoretical study on electronic properties and pressure-induced phase transition in β-CdP2

In this paper, both the local density approximation (LDA) and the generalized gradient approximation (GGA) are used to investigate the structural and electronic properties of the β modification of CdP2 (β-CdP2) at zero pressure. In addition, the energy band structure, electron density of states (DOS) and projected density of states (PDOS) analysis of β-CdP2 are presented. What is more, we study the properties of β-CdP2 in the pressure range of 0-20 GPa, show the variations of the cell volume and band gap with the pressure for both LDA and GGA approximation. Then, the bulk modulus B0 and its first pressure derivative B0′ obtained by fitting different equations of state (EOS) to the pressure-volume (P-V) relation at ambient pressure are presented and compared with the available experimental data. At the end of our study, we for the first time find that a pressure-induced structural phase transition from the tetragonal phase (β-CdP2) to a orthorhombic phase (α-CdP2) when the pressure is increased to a value between 20 and 25 Gpa in theory.