arXiv subjects

Graeme M. Day

Publications and source records attributed to Graeme M. Day.

3 recordsLinked to original sources

arXiv2024

Design of novel organic proton-transfer acid-base (anti-)ferroelectric salts with crystal structure prediction

Organic molecular ferroelectrics, including organic proton-transfer ferroelectrics and antiferroelectrics, are potentially attractive in organic electronics and have significant chemical tunability. Among these, acid-base proton transfer (PT) salts stand out due to their low coercive fields and the possibility to tune their properties with different acid-base combinations. Using crystal structure prediction, combining small acid and base organic molecular species, we here predict three novel acid-base PT ferroelectric salts with higher polarization than existing materials. We also report two combinations that form antiferroelectric crystal structures. However, some combinations also result in unfavorable packing or the formation of co-crystal or in one case a divalent salt. The protonation state is found to be highly linked to the crystal structure, with cases where salt crystal structures have the same energetic preferability as co-crystals with a different crystalline packing.

cond-mat.mtrl-sci↗

arXiv2023

Modular, Multi-Robot Integration of Laboratories: An Autonomous Solid-State Workflow for Powder X-Ray Diffraction

Automation can transform productivity in research activities that use liquid handling, such as organic synthesis, but it has made less impact in materials laboratories, which require sample preparation steps and a range of solid-state characterization techniques. For example, powder X-ray diffraction (PXRD) is a key method in materials and pharmaceutical chemistry, but its end-to-end automation is challenging because it involves solid powder handling and sample processing. Here we present a fully autonomous solid-state workflow for PXRD experiments that can match or even surpass manual data quality. The workflow involves 12 steps performed by a team of three multipurpose robots, illustrating the power of flexible, modular automation to integrate complex, multitask laboratories.

cs.RO↗

arXiv2022

Densest plane group packings of regular polygons

Packings of regular convex polygons ($n$-gons) that are sufficiently dense have been studied extensively in the context of modeling physical and biological systems as well as discrete and computational geometry. Former results were mainly regarding densest lattice or double-lattice configurations. Here we consider all two-dimensional crystallographic symmetry groups (plane groups) by restricting the configuration space of the general packing problem of congruent copies of a compact subset of the two-dimensional Euclidean space to particular isomorphism classes of the discrete group of isometries. We formulate the plane group packing problem as a nonlinear constrained optimization problem. By means of the Entropic Trust Region Packing Algorithm that approximately solves this problem, we examine some known and unknown densest packings of various $n$-gons in all $17$ plane groups and state conjectures about common symmetries of the densest plane group packings for every $n$-gon.

math.MG↗