14 Examples of How LLMs Can Transform Materials Science and Chemistry: A Reflection on a Large Language Model Hackathon

Chemistry and materials science are complex. Recently, there have been great successes in addressing this complexity using data-driven or computational techniques. Yet, the necessity of input structured in very specific forms and the fact that there is an ever-growing number of tools creates usability and accessibility challenges. Coupled with the reality that much data in these disciplines is unstructured, the effectiveness of these tools is limited. Motivated by recent works that indicated that large language models (LLMs) might help address some of these issues, we organized a hackathon event on the applications of LLMs in chemistry, materials science, and beyond. This article chronicles the projects built as part of this hackathon. Participants employed LLMs for various applications, including predicting properties of molecules and materials, designing novel interfaces for tools, extracting knowledge from unstructured data, and developing new educational applications. The diverse topics and the fact that working prototypes could be generated in less than two days highlight that LLMs will profoundly impact the future of our fields. The rich collection of ideas and projects also indicates that the applications of LLMs are not limited to materials science and chemistry but offer potential benefits to a wide range of scientific disciplines

Mechanical Properties of Symmetric Tilt Grain Boundaries in Silicon and Silicon Carbide: A Molecular Dynamics Study

The mechanical properties of polycrystalline materials are governed by the underlying microstructure. In this context, in this dissertation, the role of grain boundaries on the mechanical response of two technologically important materials namely silicon and silicon carbide are examined. In particular, the dynamics of silicon carbide and silicon symmetric tilt bicrystals under shear load are characterized via molecular dynamics simulations. Cubic silicon carbide bicrystals with low-angle grain boundaries exhibit stick-slip behavior due to athermal climb of edge dislocations along the grain boundary at low temperatures. With increasing temperature, stick-slip becomes less pronounced due to competing dislocation glide, and at high-temperatures, structural disordering of the low-angle grain boundary inhibits stick-slip. In contrast, structural disordering of the high-angle grain boundary is induced under shear even at low temperatures, resulting in a significantly dampened stick-slip behavior. When a single layer graphene sheet is introduced at the grain boundary of the symmetric tilt silicon-carbide bicrystals, the resultant shear response is dictated by the orientation of the graphene sheet. Specifically, when the graphene layer is oriented perpendicular to the gain boundary, stick-slip behavior displayed by the low-angle grain boundaries is inhibited, though both low-angle and high-angle grain boundaries exhibit displacement along crystallographic planes parallel with the applied shear direction. On the other hand, when the graphene sheet is parallel to the grain boundary, shear deformation at the grain boundary for both low-angle and high-angle bicrystals is diminished. In silicon bicrystals, high-angle grain boundaries demonstrate coupled motion, characterized by an additional normal motion of the grain boundary. Interestingly, this phenomenon was observed previously in metallic materials. Further, the grain boundary coupling factor, which is ratio of the grain boundary normal velocity to the grain translation velocity, matches the predicted geometric value. The underlying atomic scale mechanisms that govern the grain boundary coupled motion consists of concerted rotations of silicon tetrahedra within the grain boundary. For low-angle grain boundaries in silicon, the activation of dislocation glide along the predicted slip-plane takes precedence and no grain boundary coupling is observed. This behavior is similar to that of silicon carbide seen at high-temperatures but for silicon it occurs for a large temperature window.Release after 31-Jul-201

Hybrid Quantum-Classical Eigensolver without Variation or Parametric Gates

The use of near-term quantum devices that lack quantum error correction, for addressing quantum chemistry and physics problems, requires hybrid quantum-classical algorithms and techniques. Here, we present a process for obtaining the eigenenergy spectrum of electronic quantum systems. This is achieved by projecting the Hamiltonian of a quantum system onto a limited effective Hilbert space specified by a set of computational bases. From this projection, an effective Hamiltonian is obtained. Furthermore, a process for preparing short depth quantum circuits to measure the corresponding diagonal and off-diagonal terms of the effective Hamiltonian is given, whereby quantum entanglement and ancilla qubits are used. The effective Hamiltonian is then diagonalized on a classical computer using numerical algorithms to obtain the eigenvalues. The use case of this approach is demonstrated for ground state and excited states of BeH2 and LiH molecules, and the density of states, which agrees well with exact solutions. Additionally, hardware demonstration is presented using IBM quantum devices for H2 molecule

A molecular dynamics study of the role of molecular water on the structure and mechanics of amorphous geopolymer binders

In this paper, molecular dynamics simulations are used to study the effect of molecular water and composition (Si/Al ratio) on the structure and mechanical properties of fully polymerized amorphous sodium aluminosilicate geopolymer binders. The X-ray pair distribution function for the simulated geopolymer binder phase showed good agreement with the experimentally determined structure in terms of bond lengths of the various atomic pairs. The elastic constants and ultimate tensile strength of the geopolymer binders were calculated as a function of water content and Si/Al ratio; while increasing the Si/Al ratio from one to three led to an increase in the respective values of the elastic stiffness and tensile strength, for a given Si/Al ratio, increasing the water content decreased the stiffness and strength of the binder phase. An atomic-scale analysis showed a direct correlation between water content and diffusion of alkali ions, resulting in the weakening of the AlO4 tetrahedral structure due to the migration of charge balancing alkali ions away from the tetrahedra, ultimately leading to failure. In the presence of water molecules, the diffusion behavior of alkali cations was found to be particularly anomalous, showing dynamic heterogeneity. This paper, for the first time, proves the efficacy of atomistic simulations for understanding the effect of water in geopolymer binders and can thus serve as a useful design tool for optimizing composition of geopolymers with improved mechanical properties. Published by AIP Publishing.Full Published Online: October 2016; 12 month embargo.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Evolution of internal strain in austenite phase during thermally induced martensitic phase transformation in NiTi shape memory alloys

New insight into the temperature dependent evolution of internal strain in the austenite phase during the martensitic phase transformation in NiTi shape memory alloys is provided via classical molecular dynamics simulations that employ well-established interatomic potentials for NiTi. It is shown, for the first time, that the developed strain tensor in the austenite phase is tetragonal in nature, with exponential temperature-dependence. Equally importantly, it is found that the developed internal strain (parallel to the habit plane) in the austenite varies linearly with the evolving martensite phase fraction. Interestingly, the Richard’s equation is found to describe the temperature dependence of the martensite phase fraction as well as the internal strain components parallel to the habit plane in the austenite phase. An analysis of the temperature dependent phonon dispersion of strained austenite revealed the competition between phonon softening of the TA2 branch and internal strain that leads to stabilization of the austenite phase in the two phase regime.University of Arizona24 month embargo; Available online 17 March 2017This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The effect of grain-size on fracture of polycrystalline silicon carbide: A multiscale analysis using a molecular dynamics-peridynamics framework

A robust atomistic to mesoscale computational multiscale/multiphysics modeling framework that explicitly takes into account atomic-scale descriptions of grain-boundaries, is implemented to examine the interplay between grain-size and fracture of polycrystalline cubic silicon carbide (3C-SiC). A salient feature of the developed framework is the establishment of scale-parity between the chosen atomistic and the mesoscale methods namely molecular dynamics (MD) and peridynamics (PD) respectively, which enables the ability to model the effect of the underlying microstructure as well as obtain relevant new insights into the role of grain-size on the ensuing mechanical response of 3C-SiC. Material properties such as elastic modulus, and fracture toughness of single crystals and bicrystals of various orientations are obtained from MD simulations, and using appropriate statistical analysis, MD derived properties are interfaced with PD simulations, resulting in mesoscale simulations that accurately predict the role of grain-size on failure strength, fracture energy, elastic modulus, fracture toughness, and tensile toughness of polycrystalline 3C-SiC. In particular, it is seen that the fracture strength follows a Hall-Petch law with respect to grain-size variations, while mode-I fracture toughness increases with increasing grain-size, consistent with available literature on brittle fracture of polycrystalline materials. Equally importantly, the developed MD-PD multiscale/multiphysics framework represents an important step towards developing materials modeling paradigms that can provide a comprehensive and predictive description of the microstructureproperty-performance interplay in solid-state materials.24 month embargo; published online: 22 December 2018.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Agent-to-Simulant Relationships for Vapor Emission from Absorbing Materials

When using a simulant to predict the behavior of a chemical warfare agent (CWA), it is not always possible to sufficiently match all relevant properties, and the use of an agent-to-simulant relationship is required. The objective of the agent-to-simulant relationship developed here is to enable the prediction of vapor emission rate of a CWA from a polymer given an experimental measurement of the vapor emission rate of a simulant from the polymer. Vapor emission experiments for the CWA sulfur mustard (HD) and the simulants methyl salicylate (MeS) and 2-chloroethyl ethyl sulfide (CEES) absorbed in the polymers silicone and polydimethylsiloxane (PDMS) were carried out to verify the theoretical predictions. It was found that the agent-to-simulant relationship holds if the initial dimensionless concentration distributions and Biot numbers in the polymer are similar for the agent and simulant. The mathematical agent-to-simulant relationship also provides guidance on the critical properties to match in simulant selection

A molecular dynamics study of the role of molecular water on the structure and mechanics of amorphous geopolymer binders

In this paper, molecular dynamics simulations are used to study the effect of molecular water and composition (Si/Al ratio) on the structure and mechanical properties of fully polymerized amorphous sodium aluminosilicate geopolymer binders. The X-ray pair distribution function for the simulated geopolymer binder phase showed good agreement with the experimentally determined structure in terms of bond lengths of the various atomic pairs. The elastic constants and ultimate tensile strength of the geopolymer binders were calculated as a function of water content and Si/Al ratio; while increasing the Si/Al ratio from one to three led to an increase in the respective values of the elastic stiffness and tensile strength, for a given Si/Al ratio, increasing the water content decreased the stiffness and strength of the binder phase. An atomic-scale analysis showed a direct correlation between water content and diffusion of alkali ions, resulting in the weakening of the AlO4 tetrahedral structure due to the migration of charge balancing alkali ions away from the tetrahedra, ultimately leading to failure. In the presence of water molecules, the diffusion behavior of alkali cations was found to be particularly anomalous, showing dynamic heterogeneity. This paper, for the first time, proves the efficacy of atomistic simulations for understanding the effect of water in geopolymer binders and can thus serve as a useful design tool for optimizing composition of geopolymers with improved mechanical properties. Published by AIP Publishing.Full Published Online: October 2016; 12 month embargo.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Solvent-Assisted Desorption of 2,5-Lutidine from Polyurethane Films

A fundamental understanding of chemical interactions and transport mechanisms that result from introducing multiple chemical species into a polymer plays a key role in the development and optimization of membranes, coatings, and decontamination formulations. In this study, we explore the solvent-assisted desorption of a penetrant (2,5-lutidine) in polyurethane with aprotic (acetonitrile) and protic (methanol) solvents. Chemical interactions between solvent, penetrant, and polymer functional groups are characterized via time-resolved Fourier transform infrared spectroscopy (FTIR) during single and multicomponent exposures. For both solvents, an increase in the extraction rate of the penetrant is observed when the solvent is applied during desorption. Inspection of the FTIR spectra reveals two potential mechanisms that facilitate the enhanced desorption rate: (1) penetrant/solvent competition for hydrogen donor groups on the polymer backbone and (2) disruption of the self-interaction (cohesive forces) between neighboring polymer chains. Finally, the aprotic solvent is found to generate an order of magnitude greater desorption rate of the penetrant, which is attributed to a greater disruption of the self-interaction during penetrant desorption compared to the protic solvent and the inability of an aprotic solvent to form larger and potentially slower penetrant–solvent complexes