Adri van Duin

Mesoporous silica materials (MSMs) are well-suited for biomedical applications due to their unique features, including a large surface area and tunable pore size. To enhance their durability, the small pores in MSMs are filled with carbon precursors and then carbonized to prevent them from interacting with unreacted silicic acid. In this study, we synthesized and healed MSMs using a combination of non-reactive and reactive molecular dynamics (MD) simulations. The non-reactive MD simulation revealed that the self-assembly of Pluronic® L64 polymers in water resulted in nearly 80 % hydrogen bonds between the hydrophilic sections of the micelle and water. In the bond-boosted ReaxFF MD simulations, silicic acid precursors were condensed on the micelle surface, with over 60 % of them leading to the creation of periodic mesoporous silica within the system. Condensation of silicic acid precursors at 300 K with …

We present a multi-scale formalism that accounts for the formation of nano-scale bubbles/cavities owing to a burst of water molecules after the passage of high energy charged particles that leads to the formation of hot non-ionizing excitations or thermal spikes (TS). We demonstrate the coexistence of a rapidly growing condensed state of water and a hot spot that forms a stable state of diluted water at high temperatures and pressures, possibly at a supercritical phase. Depending on the temperature of TS, the thin shell of a highly dense state of water grows by three to five times the speed of sound in water, forming a thin layer of shock wave (SW) buffer, wrapping around the nano-scale cylindrical symmetric cavity. The stability of the cavity, as a result of the incompressibility of water at ambient conditions and the surface tension, allows the transition of supersonic SW to a subsonic contact discontinuity and dissipation to thermo-acoustic sound waves. We further study the mergers of nanobubbles that lead to fountain-like or jet-flow structures at the collision interface. We introduce a time delay in the nucleation of nano-bubbles, a novel mechanism, responsible for the growth and stability of much larger or even micro-bubbles, possibly relevant to FLASH ultra-high dose rate (UHDR). The current study is potentially significant at FLASH-UHDRs. Our analysis predicts the black-body radiation from the transient supercritical state of water localized in nano-cavities wrapping around the track of charged particles can be manifested in the (indirect) water luminescence spectrum.

Undergraduate research transforms student’s conceptions of themselves as scientists and encourages participation and retention in science, technology, engineering, and mathematics (STEM) fields. Many barriers exist to carrying out scientifically impactful undergraduate research in nanomaterials at primarily undergraduate institutions (PUIs). Here, we share several practices and design principles that demonstrate pathways to overcome these barriers. Design of modular research projects with low entry barriers is essential. Postsynthetic transformation of nanoparticles is a field that enables such design and has been used successfully to advance nanoscience research while being achievable within undergraduate laboratories. Relatively large, inclusive research communities can be supported through the creation of opportunities with peer- and near-peer mentoring. We also share emerging strategies for enabling …

All-inorganic halide perovskites have received a great deal of attention as attractive alternatives to overcome the stability issues of hybrid halide perovskites that are commonly associated with organic cations. To find a compromise between the optoelectronic properties of CsPbI3 and CsPbBr3, perovskites with CsPb(BrxI1–x)3 mixed compositions are commonly used. An additional benefit is that without sacrificing the optoelectronic properties for applications such as solar cells or light-emitting diodes, small amounts of Br in CsPbI3 can prevent the inorganic perovskite from degrading to a photo-inactive non-perovskite yellow phase. Despite indications that strain in the perovskite lattice plays a role in the stabilization of the material, a full understanding of such strain is lacking. Here, we develop a reactive force field (ReaxFF) for perovskites starting from our previous work for CsPbI3, and we extend this force field to …

This research presents pioneering work on transforming a variety of waste plastic into synthetic graphite of high quality and purity. Six recycled plastics in various forms were obtained–including reprocessed polypropylene, high-density polyethylene flakes, shredded polyethylene films, reprocessed polyethylene (all obtained from Pennsylvania Recycling Markets Center), polystyrene foams, and polyethylene terephthalate bottles (both sourced from a local recycling bin). The waste plastics were carbonized in sealed tubing reactors. The study shows that this versatile process can be used on a mix of waste plastics in a variety of recycled forms to obtain a uniform graphitic carbon phase, hence addressing the challenges of separation and transportation faced by the plastic recycling industry. The conversion yield to elemental carbon for recycled plastics was improved by up to 250% by using graphene oxide (GO …

We have developed a reactive force field within the ReaxFF framework to accurately describe reactions involving aluminum–molybdenum alloy, which are part parameters of Al–O–Mo ternary system metastable intermolecular composites. The parameters are optimized from a training set, whose data come from density functional theory (DFT) calculations and experimental value, such as heat of formation, geometry data, and equation of states, which are reproduced well by ReaxFF. Body-centered cubic molybdenum’s surface energy, vacancy formation, and two transformational paths, Bain and trigonal paths are calculated to validate the ReaxFF ability describing the defects and deformations. Some structures’ elastic constant and phonon are calculated by DFT and ReaxFF to predict the structures’ mechanics and kinetic stability. All those results indicate that the fitted parameters can describe the energy difference …

The interface between NiCr alloys and FLiNaK molten salt exhibits complex corrosion behavior, mainly driven by intricate chemical interactions involving Cr and F− ions. Understanding these dynamic reactions is crucial for developing effective corrosion mitigation strategies to ensure the long-term durability of Ni-based alloy components in molten salt technologies. However, obtaining molecular-level understanding through experiments is challenging. To address this, we utilize reactive molecular dynamics simulations enabled by a reactive force field, ReaxFF, to investigate detailed reaction dynamics at the atomic level. We first present the development of the ReaxFF parameter set for Ni/Cr/F/Li/Na/K based on extensive first-principles calculations. With this force field, we achieve a strong agreement for the structure of FLiNaK molten salt by comparing the pair distribution functions with experimental and simulation …

ReaxFF reactive force field bridges the gap between nonreactive molecular simulations and quantum mechanical calculations and has been widely applied during the past two decades. However, its application to earth materials, especially those under high TP conditions relevant to Earth’s interior, is still limited due to the lack of available parameters. Here, we present the development and validation of a ReaxFF force field containing several of the most common elements in Earth’s crust, ie, Si/Al/O/H/Na/K. The force field was trained against a large data set obtained from density functional theory (DFT) calculations, including charges, bond/angle distortion curves, equation of states, ion migration energy profiles, and condensation reaction energies. Different coordination environments were considered in the training set. The fitting results showed that the current force field can well reproduce the DFT data (the …