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Overview

Scientific discussion meeting organised by Professor Scott Woodley, Professor Sir Richard Catlow FRS, Professor Nora H de Leeuw and Professor Angelos Michaelides FRS.

The development of advanced materials is of central importance in key scientific and industrial areas, including energy, catalysis and quantum technologies. High end computing and data science offer unprecedented opportunities for predictive modelling of complex materials. The meeting explored the scientific and methodological challenges in the field, focusing on structure prediction, nucleation and crystal growth, biomaterials and catalysis.

The schedule of talks and speaker biographies are available below. Speaker abstracts are also available below. Meeting papers will be published in a future issue of Philosophical Transactions of the Royal Society A. 

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Enquiries: contact the Scientific Programmes team.

Organisers

Schedule


Chair

09:00-09:05
Welcome
09:05-09:35
Ab initio free energy simulations with chemical accuracy for molecule - surface interactions

Abstract

Free energy simulations require (i) a method to calculate the potential energy surface (PES), and (ii) a method to sample the potential energy. The 'standard model of computational catalysis' uses (i) DFT with some account of dispersion, and (ii) local sampling using harmonic partition functions. For adsorption of alkanes in zeolite catalysts we show that chemically accurate (within ± 4 kJ/mol) results require going beyond the 'standard model' in both respects. The researchers use their hybrid QM:QM method1 to calculate MP2-quality PES, and they use MD in configuration space to sample the PES. They present a general local approach that uses hybrid QM:QM energies for stationary points, anharmonic partition functions for local sampling, and global sampling over a lattice of sites. For example, for adsorption of CO2, CH4, N2, CO, in metal-organic frameworks, chemically accurate free energies for adsorption on individual sites serve as input for Grand Canonical Monte Carlo lattice simulations.2

1J Sauer, Acc Chem Res 52 (2019) 3502.

2 A Kundu, K Sillar, J Sauer, Chem Sci 11 (2020) 643.

Speakers

09:35-09:45
Discussion
09:45-10:15
Modelling realistic nanoporous materials at operating conditions

Abstract

Nanoporous materials used in catalysis, sorption, separations are far from perfect, they possess a broad range of heterogeneities in space and time extending over several orders of magnitude. Furthermore, their functional behaviour is largely determined by the conditions in which they do the work. Modelling realistic materials having defects, active sites at true operating conditions of temperature, pressure, etc poses a tremendous challenge. A typical modelling endeavour consists of various steps, with first construction of an atomistic model which is representative for the material. Within this respect, it needs to be emphasised that true crystals exhibit a broad range of spatial heterogeneities, ranging from the nanometer to the micrometer scale. Furthermore, realistic crystals have a finite size, with a certain morphology, which all affect their properties. Given this complexity construction of realistic molecular models for the materials is a challenge on its own. Second, one needs to select a method to determine the forces between the atoms and construct the potential energy surface. This level of theory largely determines the accessible length and time scales of current simulations. In principle one needs to use quantum mechanical methods however in this case length and time scales are restricted to the nanometer scale and molecular dynamics runs extend to a few hundreds of picoseconds, which are much too small to compare with experimental spatiotemporal windows. With classical force fields one can extend the accessible length and time scales, however one loses accuracy compared to the quantum description and the simple analytical potentials are not straightforward transferable to a broader range of thermodynamic conditions. With the fast evolution of machine learning potentials, a window of opportunity is created to simulate more realistic materials at longer length and time scales than currently accessible with accuracy comparable to the underlying quantum mechanical data from which the MLP is derived. Within this contribution, we highlight some of our recent results where we derived MLPs for nanoporous frameworks and applied the methods to describe reactive events in zeolites and to describe flexible behaviour within nanoporous materials. Finally, when having selected an appropriate level of theory to determine the PES, advanced sampling methods need to be used to efficiently explore all relevant regions of configuration space. Within Professor Van Speybroeck's group they have developed a series of methods to describe so-called rare events like reactive events, transport properties, phase transformation of nanoporous materials. Using the plethora of methods sketched above they will give some examples on how to model spatiotemporal processes in realistic nanostructured materials. Spatiotemporal processes refer to processes where the observed dynamics is entangled with the spatial heterogeneities within the material.1 Examples are taken from catalysis and diffusion within zeolites, phase transformations in metal-organic frameworks.

[1] V Van Speybroeck, S Vandenhaute, AEJ Hoffman, SMJ Rogge, Trends in Chemistry 2021, 3 (8), 605-619.

Speakers

10:15-10:30
Discussion
10:30-11:00
Coffee
11:00-11:30
Operando Catalysis - a Challenge for Computational Discovery and Data-Driven Design

Speakers

11:30-11:45
Discussion
11:45-12:15
Multi-scale Modeling and Simulations of Structural Transitions in Smart Materials

Speakers

12:15-12:30
Discussion

Chair

13:30-14:00
Multiscale Modeling in Tissue Engineering and Cancer Scaffolds

Abstract

Modeling innovations for biomaterials development is an emerging avenue for discovering next-generation materials for biomedical applications. This work presents the design of novel bone tissue engineered materials and scaffolds for large bone defects through multiscale modeling approaches bridging molecular-scale phenomena to the macroscale in polymer-clay-nanocomposites. Unique amino acid intercalations inside clay galleries guided by molecular dynamics and prediction of degradation and bone growth through mechanics-based modeling is utilised. The researchers also present the design of novel interlocking block systems for large bone defects using finite element modeling methods. Besides filling bone defects, these bone regenerating scaffolds are also used to develop cancer testbeds for prostate and breast cancer bone metastasis. Extensive experimentation of cellular responses and behaviors indicates the development of true in vitro models of bone metastasis. The testbeds are studied with commercial and patient-derived prostate and breast cancer cell lines. Modeling this complex system from adhesion proteins and cellular structural proteins to cells provides a quantitative view into the process of metastasis. Bone metastasis is the leading cause of death worldwide, with over 1 million fatalities due to breast cancer and prostate cancer. An estimated 178 million bone fractures were reported globally in 2019, and the US-CDC reports a global incidence rate for hip fracture to rise by 240% in women and 310% in men. Thus, the appropriate design of bone replacement materials is an important global issue. Innovations in modeling are likely to pave the way for positive outcomes for patients globally. 

Speakers

14:00-14:15
Discussion
14:15-14:45
From atomic units to astronomical units: multiscale modeling paradigms for unraveling the materials universe

Abstract

Multiscale materials modeling (MMM) paradigms have attained a level of maturity such that they can be reliably implemented for the discovery, design, development, and deployment of advanced materials for a wide variety of engineering and technological applications. Of equal significance is their importance as an interrogation tool for interpreting the composition-microstructure-origin inter-relations of planetary materials. In this regard, Dr Muralidharan will discuss and demonstrate the predictive capabilities of MMM not just for development of advanced materials but also for providing important insights into fundamental processes that underlie planet formation in the solar system. Specifically using unified MMM frameworks, Dr Muralidharan will highlight the intrinsic commonalities that underpin (i) the mechanics of additively manufactured parts via the cold-spray process and the mechanics of planetary accretion; (ii) open system thermodynamics of planetary materials evolution and that of natural and synthetic biocomposites; (iii) interface mediated molecular interactions that control the chemo-mechanics of geopolymer-based cements and the role of surface chemistry on the origin and delivery of prebiotic organics in planetary materials and meteoritic samples. Lessons learned from these studies have profound implications not only for pushing the frontiers of materials science, but also for setting the stage for planetary exploration and for providing a deeper understanding of how life originated in our solar system.

Speakers

14:45-15:00
Discussion
15:00-15:30
Tea
15:30-16:00
Understanding structure-property relations in biological and bio-inspired molecular crystals from first principles

Abstract

Molecular crystals are crystalline solids composed of molecules bound together by relatively weak intermolecular interactions, typically consisting of van der Waals interactions and/or hydrogen bonds. These crystals play an important role in many areas of science and engineering, ranging from biology and medicine to electronics and photovoltaics. Therefore, much effort has been dedicated to understanding their structure and properties. Here, Professor Kronik will focus on our recent progress in explaining and even predicting important classes of collective effects, ie, phenomena that the individual units comprising the crystal do not exhibit, but arise through their interaction. Specifically, Professor Kronik will demonstrate these concepts by addressing: (1) Unusual structure-function relations in biogenic molecular crystals; (2) Surprising mechanical properties of amino-acid based bio-inspired molecular crystals; (3) Unexpected magnetic and spintronic behavior in metal-organic crystals. Throughout, he will highlight the insights gained from a successful interaction between theory and experiment.

Speakers

16:00-16:15
Discussion
16:15-18:00
Poster session

Chair

09:00-09:30
Energy landscapes for predictive modelling of complex materials

Abstract

The potential energy landscape provides a conceptual and computational framework for investigating structure, dynamics and thermodynamics in condensed matter and molecular science. This talk will summarise new approaches for global optimisation, calculating thermodynamic properties in systems exhibiting broken ergodicity, and rare event dynamics. Applications will be presented that exploit generalised basin-hopping for global optimisation in continuous and discrete metric spaces, with examples ranging from biomolecules tomachine learning and quantum computing. Design principles for self-assembly of mesoscopic structures extend the single funnel paradigm to multifunnel landscapes, with the potential for encoding multifunctional materials.

 

Selected Publications:

DJ Wales, Annu Rev Phys Chem (2018) 69, 401

JA Joseph, K Röder, D Chakraborty, RG Mantell, and DJ Wales, Chem Comm 53, 6974, 2017.

DJ Wales, Curr Op Struct Biol, 20, 3-10 (2010)

DJ Wales, "Energy Landscapes", Cambridge University Press, Cambridge, 2003

 

 

Speakers

09:30-09:45
Discussion
09:45-10:15
Structure prediction in low dimensions - concepts, issues and examples

Abstract

New chemical materials and compounds serve as the foundation for the modern technology of our civilisation, where these materials should be environmentally friendly, with stable and controllable properties for a multitude of applications, and at the same time energy efficient in their synthesis. Traditionally, such materials are generated in bulk and then machined down to whatever size is needed. But such materials are also often grown in a bottom-up approach on a substrate, and in the extreme we are dealing with and aiming for low-dimensional systems with bespoke properties, where the stability of such materials often becomes an issue of concern. Among these systems, we find monolayers on surfaces or inside layered compounds, ultrathin films, nanotubes and nanowires, just to name a few, which are becoming increasingly important from a technological point of view. The ability to predict such kinetically stable and/or thermodynamically (meta)stable nanomaterials, followed by a computation of their properties and evaluation of their stability, is clearly of great value in their design and synthesis.[1] For the past three decades, the structure prediction of three-dimensional bulk crystalline compounds and their modifications[1,2] on the one hand, and of single atom clusters[3] and (bio)molecules[4] on the other hand, has shown great progress, and the computational approaches used are expected to be also applicable to low-dimensional systems.[5,6] In this presentation, Professor Schön will discuss the methodological features specific to the prediction of the latter systems,[7] together with examples of structure prediction for one-dimensional (eg, atom chains),[7] quasi-one-dimensional (eg, nanotubes),[7] two-dimensional (eg, monolayers),[5,8] quasi-two-dimensional (eg, layer-like building blocks for layered compounds),[9] and composite (eg, multi-molecule patterns on substrates)[10] systems.

 

[1] JC Schön, M Jansen, Angew. Chem Int Ed, 35:1286 (1996)
[2] SM Woodley, CRA Catlow, Nature Mater, 7:937 (2008)
[3] DJ Wales, H Scheraga, Science, 285:1368 (1999)
[4] GM Day et al, Acta Cryst B, 61:511 (2005)
[5] JC Schön, Process Appl Ceram, 9:157 (2015)
[6] SM Woodley, GM Day, CRA Catlow, Phil Trans Royal  Soc A, 378:20190600 (2020)
[7] JC Schön, in: Energy landscapes of nanoscale systems, Ed: DJ Wales, chapter 12 (Elsevier, Amsterdam, 2022)
[8] R Gutzler, JC Schön, Z Anorg Allg Chem, 643:1368 (2017)
[9] A Mahmoodabadi, M Modarresi, JC Schön, in preparation
[10] S Abb et al, Angew Chem Int Ed, 58:8336 (2019)

Speakers

10:15-10:30
Discussion
10:30-11:00
Coffee
11:00-11:30
Using Machine Learning for Transition State Analysis: Applications for Ligand Unbinding Kinetics

Speakers

11:30-11:45
Discussion
11:45-12:15
From Gomberg to graphene and beyond: new multifunctional 2D materials based on persistent radicals

Speakers

12:15-12:30
Discussion

Chair

13:30-14:00
Structural and dynamical heterogeneity of nucleation precursors: Controlling polymorph selection and nucleation efficiency

Abstract

Controlling the formation of specific polymorphs during crystallisation is of great interest in the design of materials with specific properties. However, the initial stages of nucleation and growth during solidification are still not fully understood, even for seemingly simple systems such as unary metals. Using transition path sampling, the researchers have studied the microscopic mechanisms during homogeneous nucleation in nickel. Their analysis of the path ensemble reveals that the emergence of the crystalline phase is preceded by the formation of pre-structured regions in the liquid that act as precursors. Extending their study to heterogeneous nucleation, they likewise observe a precursor-mediated crystallisation mechanism. Small seeds impact the structural characteristics of the liquid and induce the formation of precursors with specific structural hallmarks. The nucleating ability and polymorph selectivity of these templates is, therefore, not simply given by lattice mismatch and translational order but strongly linked to the seed’s ability to promote the formation of suitable precursors in the liquid. Furthermore, they have analysed the dynamical heterogeneity in the liquid which is revealed to play a key role in the nucleation mechanism. Crystallisation occurs preferentially in regions of low mobility in the supercooled liquid. These low mobility regions form before and spatially overlap with the regions of structural precursors, revealing a clear link between dynamical and structural heterogeneity in the liquid. The relationship between structural and dynamical heterogeneity in the liquid and the nucleation mechanism appears to be key in controlling essential parameters during crystallisation, including nucleation rates and polymorph selectivity. 

Speakers

14:00-14:15
Discussion
14:15-14:45
Toward the rational design of novel cryoprotectants: the long and weary computational road

Abstract

The delivery of the next generation of medical treatments such as regenerative medicine hinges on our ability to store biological material. Cryopreservation - that is, the process of freezing biological material whilst retaining its function - is our best bet to achieve that, but the state-of-the-art suffers from a number of crippling limitations. One such limitation is the rather scanty portfolio of cryoprotectants available to us: these compounds are added into the mix so as to control the formation of ice in biological matter and thus mitigate the many detrimental effects caused to cells and tissues by the growth of ice crystals. We need more effective, safer, less toxic, cheaper cryoprotectants - and yet, in the last few decades we have failed to design any valid alternative to the very few compounds (glycerol being a prominent example) that we have more or less serendipitously discovered in the by now distant past. This is because we lack the molecular-level understanding of how exactly cryoprotectants work. In this talk,  Dr Sosso will present some recent advances specific to the mechanism of ice re-crystallisation inhibition agents, ie compounds that limit the growth of ice crystals - one of the many aspects that a cryoprotectant can act upon. In particular, Dr Sosso will discuss the picture emerging from our findings in terms of the ice re-crystallisation inhibition activity of selected polymers, peptides and surprisingly small molecules as well. Whilst the ultimate goal of achieving the rational design of novel cryoprotectants might still be beyond our grasp, molecular simulations are playing an important part in getting us all there - and, the further we progress, the greater the computational demands that we will need to meet. 

Speakers

14:45-15:00
Discussion
15:00-15:30
Tea
15:30-16:00
The challenge of obtaining meaningful free energies for ion binding at surfaces from solution

Abstract

Ion binding at surfaces from solution is an important process in a variety of contexts from geochemistry through to the crystallisation of materials. Therefore, knowledge of the thermodynamics of such events is vital for predicting how systems will grow or dissolve under a set of conditions. With the advent of supercomputers and enhanced sampling methods, the determination of free energies for such adsorption processes is becoming increasingly possible, even for water where solvent exchange rates can be slow on the molecular dynamics timescale. Although numerous examples of solid-solution ion transfer can already be found in the literature, especially based on pathway-driven techniques, such as metadynamics or umbrella sampling, this presentation will examine the question of whether such information is actually meaningful or useful in the form often given? To explore the above question, this talk will focus on the widely studied example of NaCl growth from aqueous solution. Specifically, Professor Gale will consider the free energies of the kink sites relative to aqueous solution, as the correctness of the thermodynamics can be readily checked via the bulk solubility. By comparing the free energies of these sites as determined by a range of approaches, including pathway or alchemical techniques, it will be shown that wildly varying answers can be arrived at. However, after careful correction for all relevant simulation factors, such as system size and state, it will be shown that consistent and valid results can be reached by both alchemy and pathway-based methods.

Speakers

16:00-16:15
Discussion
16:15-16:00
Panel discussion

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