arXiv subjects

Frank Wendler

Publications and source records attributed to Frank Wendler.

3 recordsLinked to original sources

arXiv2026

Multiscale Modelling of Ferroelectrics using a Physics-Informed Neural Network Driven by Molecular Dynamics Data: Parameter Identification and Field Reconstruction

In multiscale modeling of ferroelectrics, combining atomistic simulation with continuum-scale phase-field models (PFM) remains a fundamental challenge. A key difficulty lies in faithfully capturing discrete atomic-level information within a continuum modeling framework, while accurately representing material behavior at the mesoscale. In this paper, a Physics-Informed Neural Network (PINN) driven by molecular dynamics (MD) data is used. The loss function of the network consists of a supervised term that fits the discrete spatial polarization distributions obtained from MD simulations of systems containing domain walls, and a physics-based term that incorporates the residuals of partial differential equations (PDEs) of steady-state PFM. To ensure stable and balanced training among the different loss components, adaptive gradient normalization (GradNorm) is used to dynamically adjust the task weights. By minimizing the total loss, the model not only reconstructs the polarization field along with the associated strain, stress, and energy landscape at the continuum scale, but also identifies critical physical parameters of the phase-field model, including the characteristic energy density, characteristic length factor, gradient energy anisotropy factor, and Landau polynomial coefficients. By using the PINN-predicted physical parameters in COMSOL Multiphysics to solve the corresponding PDEs within a finite element framework, we demonstrate that these parameters enable accurate reproduction of the ferroelectric domain structure and the associated material response, including stress/strain distributions and energy landscape. This framework provides an effective methodology for establishing multiscale connections between atomistic and continuum descriptions, and holds the potential to infer underlying physical properties directly from polarization distributions for a wide range of materials.

cond-mat.mtrl-sci↗

arXiv2024

Electric field direction dependence of the electrocaloric effect in BaTiO3

Single-crystalline ferroelectric (FE) perovskites show a large electrocaloric effect at electric field-induced phase transitions, promising for solid-state cooling technologies. However, paraelectric-FE transition temperatures are often too high for practical applications, and lower transitions are underrepresented in literature. Particularly, the role of thermal hysteresis and electric field direction on the caloric response is critical, especially for polycrystalline materials, but not yet fully understood. Using ab initio-based coarse-grained molecular dynamics simulations, we show how transition temperatures depend on the direction of the applied field. Also, we reveal that the choice of electric field direction can reduce thermal hysteresis and can adjust the temperature ranges where large and reversible caloric responses occur. Furthermore, we propose a phenomenological descriptor for the qualitative changes in transition temperature with field direction. This descriptor is valid for both BaTiO3 and PbTiO3, even though both materials show different microscopic electric field coupling. Finally, we identify favorable temperature and texturing conditions for large and reversible caloric responses in polycrystals.

cond-mat.mtrl-sci↗

arXiv2023

Monitoring the evolution of dimensional accuracy and product properties in property-controlled forming processes

As recent trends in manufacturing engineering disciplines show a clear development in the sustainable as well as economically efficient design of forming processes, monitoring techniques have been gaining in relevance. In terms of monitoring of product properties, most processes are currently open-loop controlled, entailing that the microstructure evolution, which determines the final product properties, is not considered. However, a closed-loop control that can adjust and manipulate the process actuators according to the required product properties of the component will lead to a considerable increase in efficiency of the processes regarding resources and will decrease postproduction of the component. For most forming processes, one set of component dimensions will result in a certain set of product properties. However, to successfully establish closed-loop property controls for the processes, a systematic understanding of the reciprocity of the dimensions after forming and final product properties must be established. This work investigates the evolution of dimensional accuracy as well as product properties for a series of forming processes that utilize different degrees of freedom for process control.

eess.SY↗