Monte Carlo simulations of ferroelectric properties based on a microscopic model for PVDF

Abstract

Ferroelectricity can be found in the organic vinylidene fluoride polymer (PVDF) which consists of the polar – [CH2–CF2]n – units. This material shows both orientational and electronic polarisation. Thus, the ferroelectric PVDF can be modelled by an interacting system which consists of permanent dipoles and field‐induced point dipoles. The orthorhombic dipole system is placed between two coplanar electrodes. All electrostatic dipole–dipole interactions are considered and the electrodes are taken into account using the method of image dipoles. Based on thermally activated pro‐ cesses, the permanent dipoles fluctuate in double well potentials according to the Boltzmann statistics. The numerical calculations are based on deterministic local field computations and on weighted probabilistic dynamic Monte Carlo steps. In this paper, we focus on the simulation of typical ferroelectric properties like hysteresis effects, the ferroelectric‐paraelectric phase transition at the Curie‐temperature, and the switching curves from the negative remanent polarisation to positive values. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The role of the interface in the electronic structure of adsorbed metal(II) (Co, Ni, Cu) phthalocyanines

“…16 The image dipole also has a profound influence on an adsorbate with a strong dipole, with conducting substrates tending to cause the dipole to lie along the surface normal, while for adsorbate dipoles on insulating substrates there should be a greater tendency for the dipole to reside in the plane of the surface. 17,18 If the organic substrate has a strong preferential dipole alignment, then dipole-dipole interactions occur and can overcome the influence of the substrate conductivity.…”

Energy barriers for dipole moment flipping in PVDF-related ferroelectric polymers

“…The predicted energy barriers will be a useful input to coarse-grained kinetic Monte Carlo simulations 39 for calculation polarization hysteresis loops, from which the EC temperature and entropy changes can be obtained. In such simulations, our range of energy barrier values (0.1-1.2 eV) will be enhanced by the exponential in the Boltzmann factor.…”

“…38 A material's EC temperature and entropy changes can be extracted from the Maxwell relations 2 and its polarization hysteresis loops, the latter of which can be calculated from kinetic Monte Carlo simulations. 39 The energy barriers for dipole moment flipping are critical inputs to such simulations. In this work, we will use the nudged elastic band (NEB) method to predict the transverse dipole moment flipping energy barriers of the ferroelectric polymers PVDF, P(VDF-TrFE), P(VDF-CFE), and P(VDF-TrFE-CFE).…”