title: Ferroelectricity, nonlinear dynamics, and relaxation effects in monoclinic Sn2P2S6.
abstract: An ab initio-based model of the temperature-induced ferroelectric phase transition in Sn2P2S6 (SPS) as a prototype of an unconventional ferroelectric is developed. The order parameter in SPS is found as the valley line on a total-energy surface of the zone-center fully symmetrical Ag and polar Bu distortions. Significant nonlinear coupling between order parameter and strain is observed. Monte Carlo simulations describe the additional low-temperature rearrangement in polar structure, which appears in domain boundaries, and describe the relaxation phenomena near the ferroelectric phase transition.
authors.affiliation: Institute for Solid State Physics and Chemistry, Uzhgorod National University, 54 Voloshyn St., 88000 Uzhgorod, Ukraine.
authors.forename: Konstantin Z
authors.initials: KZ
authors.lastname: Rushchanskii
authors.forename: Yulian M
authors.initials: YM
authors.lastname: Vysochanskii
authors.forename: Dieter
authors.initials: D
authors.lastname: Strauch