The Department of Applied Physics and Science Education at Eindhoven University of Technology (TU/e) is offering a PhD position as part of the RecyWax+ project, which focuses on the multiscale modelling of recycled wax for sustainable thermal storage. The project is supported by the Dutch Research Council NWO OTP programme and is led by Professors Alexey Lyulin, Heiner Friedrich, Henk Huinink (all TU/e), and Bernard Geurts (University of Twente). The research aims to develop efficient and low-cost phase change material (PCM) composites by combining multi-physics modelling and experimental validation. The core idea is to utilize waxes derived from the pyrolysis of plastic waste streams, combined with ultra-conductive graphene networks, to create compact and efficient thermal energy storage systems. These systems exploit phase transitions to store and release heat, functioning as 'heat batteries.' The PhD project will employ molecular modelling approaches, including the use of Gromacs and LAMMPS software and MARTINI-like upscaling, to characterize the molecular structure of polymer pyrolysis waste streams, optimize filler-matrix interfaces, and simulate ideal filler-filler contacts. The goal is to connect atomistic properties to macroscopic network scales, predict and enhance thermal conductivity, and develop practical strategies for improved PCM composites. Candidates should have a strong background in simulation and/or experimentation, with a degree in a relevant field such as theoretical physics, applied mathematics, mechanical engineering, materials science, scientific computing, physical chemistry, or polymer physics. Proficiency in C++ and/or Python and a solid command of English (C1 level) are required. The position offers a four-year full-time contract, with a competitive salary, benefits, and opportunities for professional development. The successful candidate will also participate in teaching activities and benefit from TU/e's international and interdisciplinary research environment. Applications should be submitted online and include a cover letter, CV, and references. The vacancy will remain open until filled, with a formal deadline of December 6, 2025.