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Timetable (DNMW01)

Optimal design of complex materials

Monday 14th January 2019 to Friday 18th January 2019

Monday 14th January 2019
09:00 to 09:35 Registration
09:35 to 09:45 Welcome from Christie Marr (INI Deputy Director)
09:45 to 10:30 Peter Palffy-Muhoray (Kent State University)
Attractive and Repulse Interactions in Dense Nematics
09:45 Chair: John Ball
10:30 to 11:00 Morning Coffee
11:00 to 11:45 Jonathan Robbins (University of Bristol)
Asymptotics of Landau-de Gennes theory
We consider the Landau-de Gennes model for nematic liquid crystals in a two-dimensional domain subject to integer-degree boundary conditions, consistent with the absence of defects, in the physically relevant regime of weak elasticity. At leading order, the minimum-energy configuration is described by the simpler Oseen-Frank theory. We obtain the next-order corrections using a Gamma-convergence approach. These turn out to be determined by an algebraic rather than a differential equation. The most important qualitative feature is the appearance of biaxiality, with strength and orientation determined by the gradient of the Frank director. The results are applied to the variational problem in which only the degree of the boundary conditions is fixed. In contrast to an analogous and well-known problem in the Ginzburg-Landau model of vortices, it is found that the energy is only partially degenerate at leading order, with a family of conformal boundary conditions, parameterised by the positions of escape points (the analogues of vortices), achieving the minimum possible energy. This partial degeneracy is lifted at the next order.

This is joint work with G di Fratta, V Slastikov and A Zarnescu.
11:45 to 12:30 Halim Kusumaatmaja (University of Durham)
Surveying Energy Landscapes: From Protein Folding to Bistable Liquid Crystal Device and Cylindrical Buckling
Given a Hamiltonian or energy functional, I will describe a suite of numerical methods designed to efficiently characterise its energy landscape. The methods allow systematic study of not only the most relevant minimum energy configurations, but also the transition pathways between any two minima, as well as their corresponding energy barriers and transition state configurations. I will then illustrate the versatility of the methods by studying three very distinct problems. First, using a multistable liquid crystal square well as an example, I will provide insights into how optimal transition pathways can be qualitatively different even though the minimum energy configurations remain similar, and how certain minima can lose stability. Second, I will study how thin cylindrical shells buckle. In particular, I will discuss the large number of minima we observe and whether we have a glassy or a structure-seeker energy landscape. Third, while efficient algorithms for cluster detection and data completion in high-dimensional spaces are well developed, considerably less is known about the reliable inference of state transition dynamics in such settings. Here I will show how we can reconstruct low-dimensional dynamical transition networks from high-dimensional static samples, and demonstrate the practical potential of our scheme for several protein folding transitions.
12:30 to 13:30 Lunch at Churchill College
14:30 to 15:15 Giacomo Canevari (BCAM - Basque Center for Applied Mathematics)
Design of effective bulk potentials for nematic liquid crystals via homogenisation
The material properties of a given nematic liquid crystal may be altered by dopants, i.e. suspended micro- to nano- particles in the nematic host. Even under weak anchoring conditions at the surface of the inclusions, and in the so-called "dilute regime" (i.e., when the total volume occupied by the inclusions is small), dopants can still have a significant effect; for instance, they can modify the nematic-isotropic transition temperature. In this talk, we consider a Landau-de Gennes model for a periodic suspension of small colloidal inclusions in a nematic host. By studying the homogenised limit, and proving rigorous convergence results for local minimisers, we compute the effective free energy for the doped material. In particular, we show that not only the phase transition temperature, but any coefficient of the quartic Landau-de Gennes bulk potential can be tuned. The talk is based on a joint work with Arghir D. Zarnescu (BCAM, Bilbao, Spain).
14:30 Chair: Mark Warner
15:15 to 16:00 Jamie Taylor (BCAM - Basque Center for Applied Mathematics)
Construction of two dimensional convex shapes from their excluded volumes
In a dilute system of spatially homogeneous system of hard, non-spherical, particles, Onsager tells us that all phase behaviour can (in principle) be derived by explained by understanding how much volume is excluded to one particle by the presence of another, given their relative orientations. In this talk, we will consider the case of two dimensional convex bodies, and describe forward and inverse problems related to evaluating their so-called excluded volume function, which depends entirely on the particle shape. In particular, we propose and analyse an algorithm which can reconstruct a convex body from an excluded volume function, although such solutions can be shown generally to be non-unique. While only providing results in the simpler two-dimensional setting, these results pave the way for design of particle shape based on desired phase behaviour properties.
16:00 to 16:15 Afternoon Tea
16:15 to 17:00 Daniel Beller (University of California, Merced)
Defect loops in 3D active nematics
Co-authors: Guillaume Duclos, Minu Varghese, Matthew Peterson, Arvind Baskaran, Aparna Baskaran, Michael Hagan (Martin A. Fisher School of Physics, Brandeis University ), Debarghya Banerjee (Max Planck Institute for Dynamics and Self-Organization, Göttingen), Federico Toschi (Department of Applied Physics, Eindhoven University of Technology), Sebastian Streichan, Zvonimir Dogic (Department of Physics, University of California, Santa Barbara), Vincenzo Vitelli (James Franck Institute and Department of Physics, University of Chicago), Robert Pelcovits (Department of Physics, Brown University), Thomas Powers (School of Engineering and Department of Physics, Brown University). Abstract: In 2D active nematics, internally driven chaotic flows are characterized by the continual production, motion, and annihilation of point defect pairs. We investigate the behavior of active nematics in 3D, for which we have developed an experimental model system of microtubules and molecular motors, as well as numerical modeling approaches. The defects characterizing chaotic flow are here curvilinear rather than point-like. We present a theoretical model predicting a certain class of closed disclination loops to be the system’s generic singularities. Through detailed analysis of experimental and numerically generated configurations, we show how our predictions of defect topology, geometry, and dynamics provide important insights into this highly complex 3D system.
17:00 to 18:00 Poster session & Wine Reception at the INI
Tuesday 15th January 2019
09:00 to 09:45 Richard James (University of Minnesota)
Materials from Mathematics
We present some recent examples of new materials whose synthesis was guided by some essentially mathematical ideas. They are materials that undergo phase transformations from one crystal structure to another, with a change of shape but without diffusion. They are hard materials, but nevertheless show liquid-like changes of microstructure under a fraction of a degree change of temperature. The underlying mathematical theory was designed to identify alloys that show low hysteresis and exceptional reversibility. The new alloys, of which Zn_45Au_30Cu_25 and Ti_54.7Ni_30.7Cu_12.3Co_2.3 are currently the best examples, do show unprecedented levels of these properties, but also raise fundamental questions for mathematical theory. Magnetoelectric properties of solids are often sensitive to lattice parameters, so they can be switched on and off at a phase transformation: briefly, multiferroism by reversible phase transformation. This switching can be combined with induction in the ferromagnetic case, or capacitance in the ferroelectric case, to yield devices that convert heat directly to electricity, without a separate electrical generator. We describe briefly the associated mathematical theory. The resulting multiferroics provide interesting possible ways to recover the vast amounts of energy stored on earth at small temperature difference. They move heat produced by natural and man-made sources from higher to lower temperature and therefore contribute negatively to global warming.
09:00 Chair: Randell Kamien
09:45 to 10:30 Francesco Della Porta (Max-Planck-Institut für Mathematik, Leipzig)
A moving mask hypothesis to select physically relevant microstructures
In this talk I present a moving mask hypotheses that can be used as a selection mechanism for physically relevant microstructures in thermally induced martensitic phase transitions. The moving mask hypotheses allows to better understand the importance of the cofactor conditions, particular conditions of supercompatibility between phases, which are believed to influence reversibility.
10:30 to 11:00 Morning Coffee
11:00 to 11:45 Ole Martin Lovvik (University of Oslo)
High-throughput search for new phase transformation materials with low hysteresis
Co-authors: Monika Løberg (University of Oslo), Nicholas Pike (University of Oslo)
Phase transformation materials (PTMs) can be used for energy harvesting of heat from low-temperature heat sources if the phase transformation is accompanied by an abrupt jump in a physical property like magnetization or polarization. In addition, the temperature hysteresis should be low in order to prevent losses. The criteria for this supercompatibility can be described in terms of the crystal structure of the phases. We are exploiting this in a new project where we are using various experimental and theoretical high-throughput techniques to search for unknown PTMs with very low hysteresis and a large change in potential energy. Some preliminary results are shown and discussed in light of the recent international progress in the field.
11:45 to 12:30 Eckhard Quandt (Christian-Albrechts-Universität zu Kiel)
Supercompatibility and its role on fatigue in shape memory materials
Functional shape memory alloys need to operate reversibly and repeatedly. This is especially crucial for many future applications such e.g. elastocaloric cooling, where more than ten million transformation cycles will be required. In recent years examples of unprecedented functional and structural fatigue resistance and lowered hysteresis in shape memory alloys have been achieved by combining conditions of supercompatibility between phases with suitable grain size and a favorable array of fine precipitates (1). The relative roles of these factors, especially in the case of the more demanding stress-induced phase transformations, will be discussed (2) also in view of elastocaloric applications. (1) Chluba, C.; Ge, W.; Lima de Miranda, R.; Strobel, J.; Kienle, L.; Quandt, E.; Wuttig, M.: Ultralow-fatigue shape memory alloy films, Science 348 (2015), 1004-1007. (2) Gu, H.; Bumke, L.; Chluba, C.; Quandt, E.; James, R.D.: Phase engineering and supercompatibility of shape memory alloys, Materials Today 21 (2018), 265-277.
12:30 to 13:30 Lunch at Churchill College
14:30 to 15:15 Angkana Ruland (Max-Planck-Institut für Mathematik, Leipzig)
Microstructures in SMA: Rigidity, Non-Rigidity and Simulations
Co-authors: Jamie M Taylor (BCAM), Christian Zillinger (USC), Barbara Zwicknagl (TU Berlin)In this talk I will discuss a striking dichotomy which occurs in the mathematical analysis of microstructures in shape-memory alloys: On the one hand, some models for these materials display a very rigid structure with only very specific microstructures, if one assumes that surface energies are penalised. On the other hand, without this penalisation, for the same models a plethora of very wild solutions exists. Motivated by this observation, we seek to further understand and analyse the underlying mechanisms. By discussing a two-dimensional toy model and by constructing explicit solutions, we show that adding only little regularity to the model does not suffice to exclude the wild solutions. We illustrate these constructions by presenting numerical simulations of them. The talk is based on joint work with J. M. Taylor, Ch. Zillinger and B. Zwicknagl.
14:30 Chair: Antonio DeSimone
15:15 to 16:00 Chantal Valeriani (Universidad Complutense de Madrid)
Designing novel functional materials made of active colloids: the role played by interactions
Active matter systems are composed of constituents that consume energy in order to move or exert mechanical forces, constantly driving themselves away from equilibrium [1]. Examples of active particles at the mesoscopic scale are living, such as bacteria, or artificial, such as active colloids [2,3] Experiments on spherical man-made self-propelled colloids have shown that active particles present interesting emergent collective properties [4–6], such as motility-induced phase separation (MIPS), involving spontaneous assembly of particles due to the persistence of their direction of motion [7]. An example of colloids undergoing MIPS under suitable conditions are Active Brownian Particles (ABP), i.e. self-propelled Brownian particles interacting with each other via a purely repulsive potential [8]. In order to design novel functional materials, one might need to gain control on the self-assembly process of active colloids. With this goal in mind, we have explored the competition between activity and a broad range of interactions in a suspension of active colloids, considering either isotropic (strongly repulsive [9], attractive [10,11], micelle-inducing potential [12]) or anisotropic (Janus-like) potential[13], unravelling the relevance of hydrodynamics [11,14] and investigating mixtures of active/passive particles [15,16,17]. REFERENCES: [1] C. Bechinger et al. Rev. Mod. Phys. 88, 045006 (2016). [2] W.F. Paxton et al. Chem. Commun. 441, 3 (2005). [3] S. Fournier-Bidoz et al. J. Am. Chem. Soc. 126, 13424 (2004). [4] S. Thutupalli, R. Seemann, S. Herminghaus New J. Phys. 13, 073021 (2011). [5] D. Nishiguchi, Masaki S. Phys. Rev. E 92, 052309 (2015). [6] I. Buttinoni, J. Bialké, F. Kümmel, H. Löwen, C. Bechinger, T. Speck. Phys.Rev. Lett. 110, 238301 (2013). [7] M.E. Cates, J. Tailleur. Annu. Rev. of Condens. Matt. Phys. 6, pp. 219-244 (2015). [8] S.Mallory, C.Valeriani and A.Cacciuto Annual review of Physical Chemistry, 69 59 (2018) [9] Diego Rogel Rodriguez, Francisco Alarcon, Raul Martinez, Jorge Ramirez, and Chantal Valeriani, in preparation (2018) [10] B. Mognetti, A. Saric, S. Angioletti-Uberti, A. Cacciuto, C. Valeriani and D. Frenkel Phys.Rev.Lett., 111 245702 (2013) [11] F.Alarcon, C.Valeriani and I.Pagonabarraga Soft Matter 10.1039/C6SM01752E (2017) [12] C.Tung, J.Harder, C.Valeriani and A.Cacciuto, Soft Matter 12 555 (2016) [13] S.Mallory, F.Alarcon, A.Cacciuto and C.Valeriani New Journal of Physics (2017) [14] F.Alarcon, E.Navarro, C.Valeriani and I.Pagonabarraga, PRE submitted (2018) [15] J.Harder, S.Mallory, C.Tung, C.Valeriani and A.Cacciuto, J.Chem.Phys. 141 194901 (2014) [16] R.Martinez, F.Alarcon, D.R.Rodiguez, J.L.Aragones and C.Valeriani, EPJE 41 91 (2018) [17] Diego Rogel Rodriguez, Francisco Alarcon, Raul Martinez, Jorge Ramirez, and Chantal Valeriani, under review JCP (2018) CO-AUTHORS: Francisco Alarcon, Raul Martinez, Juan Luis Aragones, Jorge Ramirez, Stewart Mallory, Ignacio Pagobanarraga, Angelo Cacciuto
16:00 to 16:15 Afternoon Tea
16:15 to 17:00 Barbara Zwicknagl (Technische Universität Berlin)
Microstructures in martensites: Scaling regimes and optimal domain shapes
Microstructures in martensites are often modeled variationally by singularly perturbed multiwell elastic energies. In this talk, I shall disusss recent analytical progress on the associated non-convex vector-valued energy minimisation problems. The focus will lie on scaling regimes for geometrically linear models for martensitic nuclei with small volume fraction of one martensitic variant, and on needle-like microstructures.
This talk is based on joint works with S. Conti, J. Diermeier, N. Lüthen, D. Melching, and M. Rumpf.
17:00 to 18:00 Mike Cates (University of Cambridge)
Reverse Engineering of Design Principles using Biased Dynamics
Suppose we want to create a material with a certain unusual property. One strategy is to start with a model of an existing material without that property, and bias its dynamics to sample unlikely trajectories for which the atypical property is pres ent. Looking at the biased trajectories, it may be possible to spot some choice of local interactions that would achieve the required effect. I will describe an instance of this in the realm of self-propelled spherical colloids. Here, biasing the ensemble to reduce colloidal collisions creates states in which the propulsion directions have polar order: accordingly, collisions can be reduced by introducing polar interactions. While this particular outcome is relatively obvious, the method is generalizable in principle to more complex cases where genuinely new design principles might emerge.

Coauthors: Takahiro Nemoto, Étienne Fodor, Robert L. Jack, Julien Tailleur

Reference: Optimizing active work: dynamical phase transitions, collective motion and jamming. T. Nemoto et al, arXiv 1805.02887
Wednesday 16th January 2019
09:00 to 09:45 Margarida Telo da Gama (Universidade de Lisboa)
Designing colloidal structures: fast and slow dynamics
Low-density networks of molecules or colloids form at low temperatures when the interparticle interactions are valence limited. Prototypical examples are networks of patchy particles, where the limited valence results from highly directional pairwise interactions. We combine extensive Langevin simulations and Wertheim’s theory of association to study these networks. We find a scale-free (relaxation) dynamics within the liquid–gas coexistence region, which differs from that usually observed for isotropic particles. While for isotropic particles the relaxation dynamics is driven by surface tension (coarsening), in low-density networks the slow relaxation proceeds through the formation of an intermediate non-equilibrium gel via a geometrical percolation transition. We show that the low temperature slow dynamics is universal, being observed also in the single phase region.

C. S. Dias, J. M. Tavares, N. A. M. Araujo and M. M. Telo da Gama, Soft Matter 14, 2744 (2018).
09:45 to 10:30 Pingwen Zhang (Peking University)
Defects of Liquid Crystals
Defects are local breakings of symmetry in an ordered medium, which can be found in various fields of physics such as solids, liquid crystals, astrophysics and high energy physics. Defects in liquid crystals are of great practical importance in material science and theoretical interest in physics and mathematics. In this talk, I will review the representation, modeling and computation of defects in liquid crystals. Within the Landau-de Gennes tensor model, we found a rich variety of defect patterns in topologically confined nematic liquid crystals, and the profiles of point defect and disclination line are obtained. The connection and difference between defect patterns under the tensor model and the vector model will be discussed. Finally, some conjectures and challenges are proposed to summarize the common characteristics of defects, in the hope of providing a deeper understanding of the defect pattern in nematic liquid crystals.
10:30 to 11:00 Morning Coffee
11:00 to 11:45 Randall Kamien (University of Pennsylvania)
Knitting is not knotting, but minimal manifolds make modeling fabrics fun and facile.  Tying these templates together produces a plethora of patterns.
11:45 to 12:30 Dirk Aarts (University of Oxford)
Measuring g(r) by test-particle insertion
The pair distribution function g(r) plays a central role in liquid state theory, linking structure and thermodynamics. It is typically measured by constructing a histogram of the distances between all pairs of particles, which is used in simulations and experiments where single particle coordinates can be obtained. Here, we present a novel method based on Henderson’s method [1] for measuring the cavity distribution function, going beyond our recent work on particles with hard interactions [2]. The method measures g(r) in a highly efficient way; moreover, it allows us to obtain an effective pair potential between colloidal particles in experiment.
12:30 to 13:30 Lunch at Churchill College
13:30 to 18:00 Free afternoon
19:30 to 22:00 Formal Dinner at Emmanuel College
Thursday 17th January 2019
09:00 to 09:45 Antonio DeSimone (SISSA)
Morphing and shape control: some lessons from the motility of unicellular organisms
Locomotion strategies employed by unicellular organism are a rich source of inspiration for studying mechanisms for shape control. In fact, in an overwhelming majority of cases, biological locomotion can be described as the result of the body pushing against the world, by using shape change. Motion is then a result Newton’s third and second law: the world reacts with a force that can be exploited by the body as a propulsive force, which puts the body into motion following the laws of mechanics. Strategies employed by unicellular organisms are particularly interesting because they are invisible to the naked eye, and offer surprising new solutions to the question of how shape can be controlled.

In recent years, we have studied locomotion and shape control in Euglena gracilis using a broad range of tools ranging from theoretical and computational mechanics, to experiment and observations at the microscope, to manufacturing of prototypes. This unicellular protist is particularly intriguing because it can adopt different motility strategies: swimming by flagellar propulsion, or crawling thanks to large amplitude shape changes of the whole body (a behavior known as metaboly). We will survey our most recent findings within this stream of research.


1. Rossi, M., Cicconofri, G., Beran, A., Noselli, G., DeSimone, A.:
Kinematics of flagellar swimming in Euglena gracilis: Helical trajectories and flagellar shapes.
PNAS 2017

Noselli, G., Beran, A., Arroyo, M., DeSimone, A.:
Swimming Euglena respond to confinement with a behavioral change enabling effective crawling.
Nature Physics (to appear, 2019)
09:00 Chair: Daniel Beller
09:45 to 10:30 Cyrill Muratov (New Jersey Institute of Technology)
Analysis of Novel Domain Wall Types in Ferromagnetic Nanostructures
Co-authors: Valeriy Slastikov (University of Bristol), Ross Lund (NJIT). Recent advances in nanofabrication allow an unprecedented degree of control of ferromagnetic materials down to the atomic scale, resulting in novel nanostructures whose properties are often dominated by material interfaces. Mathematically, these systems give rise to challenging problems in the calculus of variations that feature non-convex, vectorial, topologically constrained, multi-scale variational problems. Yet despite the daunting complexity inherent in the problem arising from the 21st century technological applications, rigorous variational analysis can still elucidate energy-driven pattern formation in these systems. In this talk, I will discuss several examples of variational problems emerging from models of current ferromagnetic nanostructures under development. With the help of asymptotic techniques and explicit solutions, I will give three examples in which the energy minimizing configurations may be characterized in terms of optimal one-dimensional transition lay er profiles separating magnetic domains with different magnetization orientation.
10:30 to 11:00 Morning Coffee
11:00 to 11:45 Radu Ignat (Université Paul Sabatier Toulouse III)
Symmetry in materials science models under the divergence constraint
The symmetry of the order parameter is one of the most important features in materials science.
In this talk we will focus on the one-dimensional symmetry of transition layers u in some variational
models (such as smectic liquid crystals, thin film blisters, micromagnetics...)
where the divergence div(u) vanishes.
Namely, we determine a class of nonlinear potentials such that the minimal transition layers are
one-dimensional symmetric. In particular, this class includes in dimension N=2 the nonlinearities w^2
with w being an harmonic function or a solution to the wave equation,
while in dimensions N>2, this class contains a perturbation of the standard Ginzburg-Landau potential
as well as potentials having N+1 wells with prescribed transition cost between the wells.
For that, we develop a theory of calibrations for divergence-free maps in R^N (similar to the theory of entropies
for the Aviles-Giga model when N=2).
This is a joint work with Antonin Monteil (Louvain, Belgium).
11:45 to 12:30 Luc Nguyen (University of Oxford)
Symmetry and multiple existence of critical points in 2D Landau-de Gennes Q-tensor theory
We study a Laudau-de Gennes model for liquid crystals where both the energy functional and the boundary data are invariant under the orthogonal group. In three dimensional settings, it is conjectured that minimizers break the rotational symmetry. We show however that in two dimensional settings, this no longer holds when the boundary data have no topological obstruction: the minimizers are `unique and rotationally symmetric'. As an application, we obtain existence of (multiple) non-minimizing rotationally symmetric critical points. Joint work with Radu Ignat, Valeriy Slastikov and Arghir Zarnescu.
12:30 to 13:30 Lunch at Churchill College
14:30 Chair: Luc Nguyen
14:30 to 15:15 Rodrigo Ledesma-Aguilar (Northumbria University)
Manipulating droplets on lubricant impregnated surfaces
Lubricant impregnated surfaces are bio-inspired surfaces that offer virtually no static friction to the motion of droplets. In this talk I will present experimental, theoretical and simulation results that demonstrate how droplets can be manipulated on such surfaces.
15:15 to 16:00 Nigel Mottram (University of Strathclyde)
Pressure-driven active nematics systems: possible optimisation and design methods
Active nematic fluids combine the flow-molecular orientation coupling phenomena seen in liquid crystals and the presence of internal energy generation that lead to spontaneous flow. These two effects combine to produce a fascinating non-eqiuilibrium system, in which enhanced mixing, defect creation and anihilation and active turbulence have all been observed. In this presentation we will consider a relatively simple system - pressure-driven flow in a channel - in which multiple non-trivial equilibria can be found. The interaction between the strength of activity, the applied pressure gradient and other parameters such as boundary anchoring constraints will be explored, with the aim of allowing optimisation of, for instance, the observed fluid flux. Using similar methodologies to those commonly used in the design of liquid crystal display devices, we are able to affect the fluid flux of each possible stable state and to even change the number of possible equilibria.

Co-authors: Dr Geoff McKay and Josh Walton (Strathclyde)
16:00 to 16:15 Afternoon Tea
16:15 to 17:00 Claudio Zannoni (Università di Bologna)
Realistic prediction of molecular organizations in thin organic films
The molecular organization of organic semiconductors (OSC), and in particular of those that present liquid crystal (LC) phases [1], has a strong influence on charge and energy transport, particularly at interfaces [2]. Predicting realistic morphologies and molecular organizations from chemical structure is, however, far from easy and has only recently proved doable by atomistic molecular dynamics [3-5]. The issue is further complicated in thin films, where the material is strongly affected by surface interactions, even if obtaining information on alignment and anchoring is essential to optimize the specific interfacial orientations required for different applications (e.g. for Field Effect Transistors, rather than Organic Solar Cells).
Here we show examples of the prediction of alignment and anchoring of organic functional materials (cyanobiphenyls in particular) at the interface with different substrates giving alignment parallel to the support surface e.g. for crystalline and glassy silica with different roughness [5] or polymers like PMMA or polystyrene [6]. We also show how hometropic orientations can be obtained coating the silica surface with suitable self assembled monolayers (SAM) of alkysilanes [7,8]. The importance of the film fabrication process on molecular alignment is also briefly discussed taking as an example the vapour deposition of sexithiophene (T6) on C60 [9] or pentacene on silica [10] While detailed atomistic simulations are on the way to providing reliable results for samples of the order of a few thousand molecules, going to significantly larger sizes comparable to those of real devices (e.g. 100nm thick) demands samples of the order of, say 106 molecules, which in turns requires giving up some details, using some form of coarse graining (CG). Ideally this CG procedure should provide reliable morphologies, albeit at molecular, rather than fully atomistic resolution, but also be capable of returning on demand the atomistic details needed for further charge transport calculations. Some examples will be presented of such a reversible CG approach based on modelling organic functional materials with collections of anisotropic Gay-Berne beads [11].

[1] H. Iino, T. Usui and J-I. Hanna, Nature Comm. 6, 6828 (2015)
[2] O.M. Roscioni, C. Zannoni, Molecular Dynamics Simulation and its Applications to Thin-Film Devices, in Unconventional Thin Film Photovoltaics, edited by E. Da Como, F. De Angelis, H. Snaith, A. B Walker, RSC (2016)
[3] J. Idé, R. Méreau, L. Ducasse, F. Castet, H. Bock, Y. Olivier, J. Cornil, D. Beljonne, G. D’Avino, O. M. Roscioni, L. Muccioli, C. Zannoni, JACS, 136, 2911 (2014)
[4] M. F. Palermo, L. Muccioli, C. Zannoni, PCCP, 17, 26149 (2015)
[5] O. M. Roscioni, L. Muccioli, R. G. Della Valle, A. Pizzirusso, M. Ricci, C. Zannoni, Langmuir, 29, 8950 (2013).
[6] M.F. Palermo, F. Bazzanini, L. Muccioli, C. Zannoni, Liq. Cryst. 44, 1764 (2017)
[7] A. Mityashin, O.M. Roscioni, L. Muccioli, C. Zannoni, V. Geskin, J. Cornil, D. Janssen, S. Steudel, J. Genoe, P. Heremans, ACS Applied Materials & Interfaces, 17, 15372 (2014)
[8] O. M. Roscioni, L. Muccioli, C. Zannoni, ACS Applied Materials & Interfaces 9, 11993 (2017).
[9] G. D'Avino, L. Muccioli and C. Zannoni, Adv. Funct. Mater. 25, 1985 (2015).
[10] O. M. Roscioni, G. D'Avino, L. Muccioli and C. Zannoni, J. Phys. Chem. Lett. 9, 6900 (2018).
[11] M. Ricci, O. M. Roscioni, L Querciagrossa, C. Zannoni. to be published (2019)
Friday 18th January 2019
09:00 to 09:45 John Ball (Heriot-Watt University)
Remarks on polycrystalline microstructure
The talk will discuss some questions related to the understanding of microstructures arising from martensitic phase transformations, and the role of compatibility across grain boundaries, drawing on joint work with Carsten Carstensen (Humboldt University, Berlin).
09:00 Peter Palffy-Muhoray
09:45 to 10:30 Dmitry Golovaty (University of Akron)
Interfaces with singularities: understanding phase transitions in nematic liquid crystals
Experimental data indicates that the nematic-to-isotropic phase transition in liquid crystals may proceed via evolution of interfaces that are not smooth. In this talk, our goal is to provide a possible explanation for the observed singularities of the phase boundaries.

In order to develop an initial understanding of transitions between the ordered and disordered states, we formulate a simple toy model based on the modified Ginzburg-Landau-type energy defined over vector fields on the plane. The corresponding variational model consists of anisotropic gradient terms and a potential that vanishes on two disconnected sets.

The principal observation from the study of the simplified model is that the phase boundary singularities can be explained by large disparity between the elastic constants in the gradient contribution to the energy. In the talk we will present a combination of rigorous analysis and numerics that leads to this conclusion. This is a joint work with Michael Novack, Peter Sternberg, and Raghavendra Venkatraman.
10:30 to 11:00 Morning Coffee
11:00 to 11:45 Alenka Mertelj (Jozef Stefan Institute)
Polar order in liquids
Polar order, i.e., ferromagnetic or ferroelectric, in 3D liquids is experimentally rarely observed. In this talk I will discuss the reason for this and show two examples of how shape of constituents can promote polar order. The first example is a ferromagnetic liquid phase, which emerges in a suspension of magnetic nanoplatelets in isotropic solvent as a result of platelets’ shape. The second example is antiferroelectric splay nematic phase, which appears in materials made of wedge-shaped molecules with large electric dipole moments.
Co-Authors: Darja Lisjak1, Patricija Hribar Boštjančič1, Borut Lampret1, Luka Cmok1, Žiga Gregorin1, Natan Osterman1, Nerea Sebastian1, Martin Čopič1, Joachim Kohlbrecher2, Juergen Klepp3, Richard J. Mandle4, Rachel R. Parker4, Adrian C. Whitwood4, John W. Goodby4
1J. Stefan Institute, Slovenia; 2PSI Villigen, Switzerland; 3University of Vienna, Austria; 4University of York, UK
11:45 to 12:30 Mark Warner (University of Cambridge)
Microstructure for continuous and localised intrinsic curvature creation
12:30 to 13:30 Lunch at Churchill College
University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons