Study of the electronic, elastic, piezoelectric and infrared properties of trigonal BPO4

Abstract

Trigonal BPO4 is a crystal crystallizing in α-quartz structure, but most fundamental properties of it are still not well studied. In this work, first principles calculations are carried out to study its electronic, elastic, piezoelectric and infrared properties. Calculated electronic properties reveal that trigonal BPO4 is an indirect band gap insulator with a gap of 7.32 eV. The top of its valence band is mainly composed of the O 2p orbital while the bottom of the conduction band is chiefly formed by the p orbitals of the B and P atoms. Orbital hybridization exists between the B(P) and O atoms. Studies on its elastic properties indicate that trigonal BPO4 is mechanically stable but anisotropic. The two independent piezoelectric constants of trigonal BPO4 are predicted to be 0.13 C/m2 for e11 and 0.04 C/m2 for e14. Simulated infrared spectrum uncovers five peaks with a relative intensity larger than 0.1 although its has forty-three infrared-active modes. The vibrational manners of these modes are sketched and the origins of their intensities are unveiled. Besides, its bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, Born effective charges and dielectric constants are also calculated and discussed.