New Quantum Mechanics Based Force Field for Describing Dynamics and Piezoelectric Properties for Various Phases of Poly(vinylidene) Fluoride Polymer

Polyvinylidene fluoride (PVDF) composites have emerged as materials of great interest for many applications due to their diverse piezoelectric, pyroelectric, and mechanical properties. To enable studies on PVDF and its modifications for new applications as sensors and actuators, we developed a new force field (PVDF-FF) that accurately predicts the elastic, dielectric, and piezoelectric properties of the four experimentally characterized phases of PVDF. The PVDF-FF was derived by fitting the force field parameters to the quantum mechanics structure and properties of the beta crystal form in such a way that it was also accurate for the other three phases. This PVDF-FF is based on the UFF universal force field, which is a simple generic force for the entire periodic table (up to Z = 103). Thus, it is compatible with combining PVDF with other materials, for example, in multifunctional applications for devices using PVDF as a piezoelectric switch, sensor, or actuator. This approach for obtaining a single UFF-based force field capable of describing the structural energetic, mechanical, dielectric, and piezoelectric performance of the α, β, γ, and δ phases of PVDF should be useful for developing other complex multifunctional materials.