The nature of anharmonicity and phase transition in SbSBr crystal

Abstract

The ferroelectric crystal structure of SbSBr is composed of [Sb(S, Br)] 1 chains parallel to the [001] axis. In paraelectric phase, the crystal structure is disordered. The theoretical investigation of dependence of potential energy V P (z) of Sb atoms on amplitudes of B 1u vibration symmetry coordinates along c(z)-axis have showed that each atom is shifted from the xy mirror plane by Dz up or down along [001]. The theoretical investigation of the average potential energy V P ðzÞ of all Sb atoms in unit cell revealed that in paraelectric phase in region of phase transition V P ðzÞ has double-well shape. This strong anharmonicity of V P ðzÞ is created by interaction between phonons.

Piezoelectric Properties of Ferroelectric SbSBr Crystal

“…At temperatures T≈T C Sb atoms average potential energyV P (z) depends on amplitude of normal coordinates of B 1u (A u ) symmetry soft mode in paraelectric phase which have double -well form. At T CVP (z) of SbSI and SbSBr have very strong dependence on temperature and deformation [4,6,7].…”

“…SbSI and SbSBr have been extensively studied because they have phase transitions and technological applications as microwave and piezoelectric devices [1][2][3][4][5][6][7]. The crystal structure of SbSBr was investigated by Cristofferson et al [8] and Inushima [9] at temperatures 294 K, 150 K, 60 K, 30 K and 11 K. SbSBr and SbSI has an orthorhombic structure and has four SbSBr molecules (12 atoms) in a unit cell.…”