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| Sami Al-Izzi | UNSW | YouTube
Shear-driven Instabilities of Membrane Tubes |
| Abstract: Motivated by the mechanics of dynamin-mediated membrane tube fission, we analyze the stability of fluid membrane tubes subjected to shear flow in azimuthal direction [1]. We find a novel helical instability driven by the membrane shear flow which results in a nonequilibrium steady state for the tube fluctuations. This instability has its onset at shear rates that may be physiologically accessible under the action of dynamin and could also be probed using in vitro experiments on membrane nanotubes, e.g., using magnetic tweezers. We discuss how such an instability may play a role in the mechanism for dynamin-mediated membrane tube fission.
[1] - S. C. Al-Izzi, P. Sens & M. S. Turner, Phys. Rev. Lett. 125, 018101 (2020)
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| Jabr Aljedani | University of Adelaide | YouTube
Multi-layer graphene folds supported on a substrate |
| Abstract: A mathematical model is developed to study the folding behaviour of multi-layer graphene sheets supported on a substrate. The conformation of the fold is determined from variational considerations based on two energies, namely the graphene elastic energy and the van der Waals (vdW) interaction energy between graphene layers and the substrate. The model is nondimensionalized and variational calculus techniques are then employed to determine the conformation of the fold. The Lennard-Jones potential is used to determine the vdW interaction energy as well as the graphene-substrate and graphene-graphene spacing distances. The folding conformation is investigated under three different approximations of the total line curvature. Our findings show good agreement with experimental measurements of multi-layer graphene folds from the literature.
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| Julie Aufort | Curtin University | |
| Supriya Bajpai | Monash University | YouTube
Cell polarity and motility dynamics coupled with intercellular signaling controls developmental patterning |
| Abstract: Cell polarity, motility and intercellular signaling in tissues plays a very important role during the development of multicellular organisms. Intercellular signaling interactions regulate cell motility and cell polarity by allowing cells to communicate with each other by transmitting signals. A key question is how the cell motility, cell polarity and intercellular signaling coupled together, influence the spatiotemporal developmental patterns in tissues. On the one hand, the motility of cells coupled with their polarity can lead to collective motion patterns. On the other hand, intercellular signaling is responsible for generating spatial developmental patterns. Although modeling efforts have, thus far, these two processes separately, experiments in recent years suggest that these processes influence each other. Hence, we present a model to study how the dynamics of cell motility and intercellular signaling coupled with cell polarity influence the spatiotemporal developmental patterns. We observe a rich variety of spatiotemporal developmental patterns that are influenced by the cell motility, polarity and intercellular signaling dynamics of the cells. We also observe that the collective motion of signaling patterns is due to the combined effect of the individual cell motion and spatiotemporal shift in signaling molecules that leads to an emergent time-scale of spatial rearrangement of the patterns.
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| Ardeshir Baktash | University of Queensland | |
| Sanjeeva Balasuriya | University of Adelaide | Coherence in nonequilibrium motion in a continuum (invited talk) |
| Abstract: In many fluid dynamics applications, particles move according to an unsteady (nonequilibrium) velocity field. Typically, this results in some groups of particles moving "coherently" (for example, in jets or vortices, such as in the Gulf Stream or the Antarctic Circumpolar Vortex), while others display strong disorder (via mechanisms such as chaotic mixing and/or turbulence). This simultaneous combination of behaviours is typically observed in realistic flows ranging from microfluidic to geophysical scales, and a key difficulty in separating coherence from incoherence is that fact that all structures are moving in a nonequilibrium fashion. Detecting regions in this way is associated with the term "Lagrangian coherent structures," where "Lagrangian" is from the fluid mechanics nomenclature for "following the flow." Analogous issues arise in other continuum mechanics applications (flow in porous media, soft matter, solid mechanics, etc), but are less studied from this perspective. In this talk, I will survey some issues and methods for detecting coherence in such nonequilibrium situations. These include finite-time Lyapunov exponents (which are based on stretching of fluid elements), stochastic sensitivity (based on uncertainty quantification of eventual locations, and is connected to the Fokker-Planck equation which governs the evolution of the probability density of particles), and seeking coherence associated with chemical or energy density which is transported by a nonequilibrium flow velocity.
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| Stefano Bernardi | University of Sydney | |
| Debra Bernhardt | University of Queensland | |
| Suresh Bhatia | University of Queensland | Simulation of Structure and Gas Transport at the Polymer-Zeolite Interface (invited talk) |
| Abstract: Mixed matrix membranes (MMM) have attracted much recent attention as materials for gas separation due to their outstanding performance, exceeding the Robeson upper bound. Such membranes are conventionally prepared by incorporating inorganic fillers such as graphene, zeolite, silica, carbon nanotubes and metal organic framework in a bulk polymer matrix. However, the ultimate success of these advanced membranes depends on the material selection and interface defect elimination. Hence, nanoscale understanding of polymer structure near a surface and gas transport at the interface is critical to the design of these advanced gas separation technologies.
Here we report a comparison of the adsorption and transport characteristics of pure component CO2 and CH4 in polyimide (PI), MFI zeolite/ZIF-8 filler and a PI-MFI zeolite/ZIF-8 composite membrane using equilibrium Molecular Dynamics (EMD) simulations. Incorporation of MFI zeolite in PI results in the improvement of kinetic selectivity of CO2 over CH4. Further, the results indicate the existence of a densified polymer region at the polymer-zeolite interface, having thickness around 1.2 nm, in which gas transport is about an order of magnitude slower than in the bulk polymer; this offers an extra resistance to gas diffusion. Zeolite crystal size has little effect on the polymer structure and gas transport at the polymer-filler interface. On the other hand nanoscale voids are found at the polymer-ZIF-8 interface, which are detrimental to selectivity. To extract gas adsorption isotherms, we implemented a two-step methodology involving coupled GCMC and NPT-EMD simulations, considering the dynamics and structural transitions in the polymer matrix upon gas adsorption, and investigated the isotherms of CO2, CH4 in pure and composite polymer membranes. The sorption results indicate that incorporation of MFI zeolite in PI improves the adsorption selectivity of CO2 over CH4. In the case of the PI-ZIF-8 system, use of an ionic liquid to fill the nano-voids is found to improve performance of the composite. We have also developed a procedure for multiscaling these results, by membrane scale simulations using the isotherms and transport properties from the molecular dynamics simulations. These simulations demonstrate significant increase in permeability with increase in CO2/CH4 selectivity for the hybrid system, as compared to the properties of the pure PI polymer membrane. The methodology developed here offers an attractive option for the in silico design of mixed matrix membranes specific to a given application.
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| Richard Bowles | University of Saskatchewan | |
| Gary Bryant | RMIT University | |
| Pierluigi Cesana | Kyushu University | |
| Nathan Clisby | Swinburne University of Technology | |
| Karen Corbett | Monash University | YouTube
Temperature Replica Exchange Molecular Dynamics Simulations of Cyclic Peptides |
| Abstract: Cyclic peptide conformations and their relative populations are major determinants of the peptide’s biological and pharmaceutical function. The characterization of low population cyclic peptide conformations is challenging, both experimentally and in unbiased molecular dynamics simulations. Temperature replica exchange molecular dynamics (TREX) simulations can enable the study of low population states. Here, we use TREX simulations to study the conformational ensemble of several cyclic hexapeptides. We validate the most populous peptide conformations of our TREX simulations against their corresponding nuclear magnetic resonance spectroscopy structures. Moreover, we report novel low-population conformations for these cyclic hexapeptides.
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| Barry Cox | University of Adelaide | |
| Peter Daivis | RMIT University | YouTube
Anisotropic heat flow in shearing fluids |
| Abstract: By simulating a simple fluid in a channel bounded by tethered atoms, the heat flux is computed for two systems: a temperature driven one with different temperatures at the walls and no flow and a wall driven, planar shear flow system. The results for the wall temperature driven system give the Fourier’s law thermal conductivity, which is shown to agree well with experiments. Through comparison of the two systems, we quantify the additional components of the heat flux parallel and normal to the walls due to shear flow.
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| Hor Dashti | Korea Institute for Advanced Study | YouTube
Competing Universalities in Non-Equilibrium Growth Models |
| Abstract: We report on the universality of height fluctuations at the crossing point of two interacting 1-dimensional KPZ interfaces with curved and flat initial conditions. We introduce a control parameter p as the probability for the initially flat geometry to be chosen and compute the phase diagram as a function of p. We find that the distribution of the fluctuations converges to the Gaussian orthogonal ensemble (GOE) Tracy-Widom (TW) distribution for p<0.5, and to the Gaussian unitary ensemble (GUE) TW distribution for p>0.5. For p=0.5, the behavior is governed by emergent Gaussian statistics in the universality class of Brownian motion.
We propose a phenomenological theory to explain our findings and discuss the possible applications in non-equilibrium transport and traffic flow.
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| Baris Demir | University of Queensland | |
| Ian Douglass | Roskilde University | YouTube
Entropy estimation using data compression |
| Abstract: Determining the entropy of a system is useful in many simulation-related contexts, including determining phase stability, optimal protein folding, and the prediction of liquid dynamics. However, an accurate evaluation generally requires multiple simulations along some path from a known starting point to use in thermodynamic integration. In this work, we take an information theoretical approach to determining the thermodynamic entropy, and present a strong quantitative relationship between compression size and excess entropy in the single-component LJ fluid over a large density-temperature range. From this, we can predict the entropy of such a system from a single simulation, or even a single configuration.
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| Timothy Duignan | University of Queensland | YouTube
The surface potential is key to explaining ion specific bubble coalescence inhibition |
| Abstract: Some salts have the peculiar ability to inhibit the coalescence of bubbles when added to solution. This is believed to be attributable to the enhancement or depletion of ions at the interface. However, this phenomenon is known to depend on which particular pairs of ions are present in a peculiar and unexplained way. Here, a modified Poisson-Boltzmann model is used to demonstrate that these rules are attributable to the fact that certain combinations of ions create a substantial surface potential in order to satisfy the electro-neutrality condition. This surface potential acts to dampen the natural propensity of these ions for the interface in a way that explains the combining rules.
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| Kirill Glavatskiy | University of Sydney | |
| Cecilia González-Tokman | University of Queensland | Limit theorems for non-autonomous dynamical systems (invited talk) |
| Abstract: Limit theorems describe fine properties of the long term statistical behavior of dynamical systems, including long term averages of observables, large deviations and fluctuations. In this talk, we present a recent approach, based on spectral methods and modern ergodic theory for transfer operators, to establish limit theorems for a class of non-equilibrium systems, called non-autonomous dynamical systems.
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| Eirini Goudeli | University of Melbourne | YouTube
Settling rate of nanosized fractal-like agglomerates |
| Tim Gould | Griffith University | van der Waals Dispersion theory in nanostructures (invited talk) |
| Abstract: I will discuss the modern theory of van der Waals dispersion forces that connects "chemist" approaches with "physicist" approaches in a seamless interpretative fashion. I will show examples where non-additivity leads to fundamental differences from standard "sum over C6" and talk about the broad conditions that lead to unusual effects. I will introduce high-quality modern theories that deal with most of these effects in a reasonably efficient way.
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| Ellie Hajizadeh | University of Melbourne | |
| Peter Harrowell | University of Sydney | The Kinetics of Crystal Growth: Mapping the Path of Structural Transformation (invited talk) |
| Abstract: The thermodynamic explanation of order appearing in a many-body system is typically straightforward – the ordered configuration corresponds to the groundstate so that, no matter how complex the structure, it will inevitably correspond to the lowest free energy state for a sufficiently low temperature. What can verge on the miraculous, however, is how a disordered system of particles manages to identify and respond to this thermodynamic directive based on the scant information accessible to a typical trajectory. The kinetics of crystal growth provides a tractable window onto the kinetics of ordering. In this talk, we will briefly review theories of the kinetics of crystal growth before outlining our recent work on the role of the interfacial groundstates on the kinetics of crystal growth.
References
G. Sun, J. Xu and P. Harrowell, The mechanism of the ultrafast crystal growth of pure metals from their melts, Nature Mat. 17, 881 (2018)
A. Hawken, G. Sun and P. Harrowell, Role of interfacial inherent structures in the fast crystal growth from molten salts and metals, Phys. Rev. Mat. 3, 043401 (2019)
G. Sun, A. Hawken and P. Harrowell, The displacement field associated with the freezing of a melt and its role in determining crystal growth kinetics. Proc. Nat. Acad. Sci. 117, 3421 (2020)
G. Sun and P. Harrowell, Crystal growth rates and liquid dynamics at the crossover between stable crystal phases. J. Chem. Phys. 152, 164505 (2020)
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| Mohammad Rashedul Hasan | University of Sydney | |
| David Huang | University of Adelaide | YouTube
Scaling of concentration-gradient-driven flow through a 2D membrane |
| Abstract: Transport of liquid mixtures through porous membranes is central to processes such as desalination, chemical separations, and energy harvesting, with ultrathin membranes made from novel 2D nanomaterials showing exceptional promise. I will present the first general theory of fluid flow through an ultrathin membrane driven by a solute concentration gradient, which predicts how solute and solvent fluxes are controlled by important microscopic parameters such as pore size and the strength and range of fluid-membrane interactions. The theory is quantitatively accurate, as shown by comparisons with continuum and molecular dynamics
simulations, and predicts markedly different flow behaviour compared with that through a thick membrane. These results have broad implications for fluid-flow processes through membranes of molecular thickness.
References:
[1] D. J. Rankin, L. Bocquet, D. M. Huang, J. Chem. Phys. 151, 044705 (2019)
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| Michelle Hunter | University of Queensland | |
| Mohammad Imaran | Monash University | YouTube
Morphodynamics of invasion of a soft substrate by self-propelled rods |
| Abstract: The colonization of a soft passive material by active, motile cells such as bacteria or cancer cells is a common scenario in biology. The resulting colonies of the invading cells are often observed to exhibit intricate patterns whose morphology and dynamics can depend on a number of factors, particularly the mechanical properties of the substrate and the motility of the individual cells. It has been suggested that this may be a form of stigmergy, wherein cells collectively coordinate over large length and time scales through interactions with their mechanical environment to colonize it optimally.
We show that the tendency of active (self-propelled) particles to form clusters of different kinds is crucial for understanding the morphodynamics of colonization. We propose a minimal 2D model consisting of self-propelled rods interacting with a passive compliant medium consisting of particles that offer elastic resistance before being plastically displaced from their equilibrium positions.
Interestingly, we find that the rate at which the colony edge advances depends non-monotonically on substrate stiffness. At any given particle activity, a distinct maximum in the colonization rate is obtained at a particular value of stiffness. We find that this non-monotonicity is due to the dynamics of vanguard clusters that form at the leading edge. The speed of these clusters depends on their shape and size which in turn depend on substrate stiffness and particle activity. These suggest that, in biological systems, particle motility may be tuned to maximize the colonization rate, given the stiffness of the surrounding substrate.
Further, as the particles move through the plastic substrate, they create furrow networks, just as in real bacterial colonies. We show that these networks have a fractal-like structure whose dimension varies systematically with substrate stiffness but is less sensitive to particle activity.
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| Jayendran Iyer | University of Queensland | |
| Ravi Jagadeeshan | Monash University | YouTube
Dynamic signatures of gelation in associative polymer solutions |
| Abstract: Solutions of associative polymers form reversible gels and networks at moderately low concentration by physical cross-linking of sticky groups distributed along the backbone of polymer chains. There are several static signatures of gelation in these systems based on the percolation transition [1], the free-chain concentration [2] and cluster-size distribution [3]. However, the relationship between these static measures and the dynamics and rheological response of associative polymer solutions remains unresolved. As a result of the formation of complex topologies in these polymer solutions, the relaxation behaviour is far more complicated than can be explained by a simple Maxwell model. In this work we have carried out multi-chain Brownian dynamics simulations to examine the dynamics and viscoelastic behaviour of multi-sticker associative polymer solutions at finite concentrations. The decay of the end-to-end vector and the stress auto-correlation functions are used to extract the relaxation time as a function of concentration. The latter is also used to determine the frequency dependence of the oscillatory shear flow material functions G' & G'', and the scaling of zero-shear rate viscosity with concentration. The evolution in these viscoelastic properties are compared with the static measures of gelation to identify which metric best correlates with the dynamic signatures of gelation.
[1] D. Stauffer, A. Aharony, Introduction to Percolation Theory, 1992.
[2] A. N. Semenov, M. Rubinstein, Macromolecules, 31, 1373-1385, 1998.
[3] S. K. Kumar, J. F. Douglas, PRL, 87 (18), 188301, 2001.
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| Owen Jepps | Griffith University | |
| Ilias Kachapov | University of Auckland | |
| Emily Kahl | University of Queensland | |
| Matthew King | Griffith University | |
| Solvej Knudsen | Roskilde University & Swinburne University of Technology | |
| Kiran Kumari | Monash University | YouTube
Computing the spatial organization and dynamics of chromatin domains |
| Abstract: The three-dimensional organisation of chromatin, on the length scale of a few genes, is crucial in determining the functional state—accessibility and amount of gene expression—of the chromatin. Recent advances in chromosome conformation capture experiments provide partial information on the chromatin organisation in a cell population, namely the contact count between any segment pairs, but not on the interaction strength that leads to these contact counts. However, given the contact matrix, determining the complete 3D organisation of the whole chromatin polymer is an inverse problem. In this work, a novel inverse Brownian dynamics method based on a coarse-grained bead-spring chain model has been proposed to compute the optimal interaction strengths between different segments of chromatin such that the experimentally measured contact count probability constraints are satisfied. Applying this method to the a-globin gene locus in two different cell types, we predict the 3D organisations corresponding to active and repressed states of chromatin at the locus. We characterise various static and dynamic properties.
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| Yawei Liu | University of Sydney | YouTube
Chiral Twist in Monolayer Assemblies of Rod-like Colloids |
| Abstract: Using Brownian dynamics simulations we study chiral monolayer assemblies formed by monodisperse hard rod-like colloidal particles in the presence of non-adsorbing polymers . Simulations show that (achiral) straight rods can assemble into monolayers with a spontaneous twist in either left- or right-handed, while chiral rods (i.e. helices) lead to assemblies with various chiral features, depending on their handedness and curliness. We find that the onset of the chirality in these assembled monolayers can be traced back to small clusters formed at the initial stage of the self-assembly. Depending on the geometry of constituent rods, the chrial twist in these microscopic monolayers is driven by the entropy gain from polymers, or rods, or both. Moreover, both the surface area and the volume of monolayers can significantly decrease or increase due to the twisting, and thus the continuum-based description breaks down at the microscopic scale. We also show that the rod fluctuations perpendicular to the monolayer plane play a crucial role in the stability of the chiral twists.
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| Tommaso Lo Giudice | University of Queensland | |
| Debora Monego | Columbia University | |
| Ashwin Nandagiri | Monash University | |
| Jordan Orchard | Swinburne University of Technology | YouTube
Escape from a polygonal billiard |
| Abstract: We have studied a class of polygonal billiard channels for their transport properties and escape dynamics. We identify apparent stability in the transport for irrational channels with finite channels of rational type presenting extreme values in the mean exit time and large time scaling of the survival probability.
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| Charlotte Petersen | University of Queensland | YouTube
Nanoscale control of competing interactions and geometrical frustration in a 2D spin ice analogue |
| Abstract: Artificial spin ice consists of interacting magnet islands arranged on a two-dimensional lattice. A key feature is the ability to precisely control the geometry, allowing the manufacture of highly frustrated systems that are hindered from minimising their local interactions. We present a new lattice geometry where the balance of competing interactions between nearest-neighbour spins can be controlled directly. This allows for tuning of the geometrical frustration in the system. By varying the lattice parameters, we observe that the system either accesses a long-range ordered ground state, or under the same conditions, remains trapped in a disordered state characterised by short-range correlations.
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| Isaac Pincus | Monash University | YouTube
Viscometric Functions and Rheo-optical properties of Dilute Polymer Solutions: Comparison of FENE-Fraenkel Dumbbells with Rodlike Models |
| Paolo Raiteri | Curtin University | |
| Kailasham Ramalingam | IITB-Monash Research Academy | YouTube
Rouse model with fluctuating internal friction |
| Abstract: Rouse model with fluctuating internal friction
[R. Kailasham, Rajarshi Chakrabarti and J. Ravi Prakash]
Conformational transitions in polymer molecules are impeded by solvent molecules, and sometimes additionally by intramolecular interactions, the resistive effects of which are collectively termed as internal friction [1]. The macroscopic consequences of internal friction are observed in both biophysical and rheological contexts, such as the damping of reconfiguration times in proteins [2], and instantaneous stress jumps at the inception of shear flow [3]. Coarse-grained polymer models for internal friction include a dashpot, in parallel with the spring, which captures the resistive force proportional to the time-rate of change of the con- nector vector between the beads. An exact solution to this model has so far been unavailable, except for the simplest case of a dumbbell (two-bead chain), due to the coupling of bead velocities. By expanding the scope of an existing methodology [3] for velocity-decoupling, the exact set of governing stochastic differential equations for a bead-spring-dashpot chain with more than two beads, and its numerical solution using Brownian dynamics, is presented for the first time. This solution is used to: (a) obtain predictions for material functions in simple and oscillatory shear-flow, and (b) address the importance of fluctuations in the modeling of internal friction, given that the most widely used theoretical framework [4] for interpreting the effects of internal friction in biomolecules relies on a pre-averaged treatment of the phenomenon. The inclusion of internal friction results in a non-monotonous variation of the viscosity with shear rate, with the occurrence of continuous shear-thickening follow- ing an initial shear-thinning regime. Furthermore, it is observed that the consequences of neglecting fluctuations in internal friction are less pronounced at equilibrium, but become more severe in the presence of a flow-field.
References:
[1] C. W. Manke and M. C. Williams, Macromolecules 18, 2045 (1985).
[2] A. Soranno et al., Proc. Natl. Acad. Sci. U.S.A. 109, 17800 (2012).
[3] C. W. Manke and M. C. Williams, J. Rheol. 31, 495 (1988).
[4] B. S. Khatri and T. C. B. McLeish, Macromolecules 40, 6770 (2007).
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| Prabhakar Ranganathan | Monash University | |
| Madhuranga Rathnayake | University of Sydney | YouTube
Evaluation of the AMOEBA force field for simulating metal halide perovskites in the solid state and in solution |
| Abstract: Organometallic halide perovskites show a promising future as an efficient and low-cost alternative for conventional photovoltaics. Devices with power conversion efficiencies over 20% have already been reported. Solution processability, high absorption coefficient and tunable bandgap make hybrid perovskites a promising alternative to silicon-based photovoltaics. However, further development is necessary before perovskite solar cells can be widely adopted by industry. For instance, they cannot currently be printed at scale. Even though a wide variety of specific fabrication methods exist to make hybrid perovskites with desired properties and composition, a molecular-level understanding of how they crystallise from solution is still lacking. Ab initio molecular dynamics simulations have been used to obtain atomistic insight into some of these processes, but are limited to timescales of the order of 10s of ps. In contrast, processes on much longer timescales have been successfully studied using classical force fields for both organic and inorganic systems. A couple of attempts have been made recently to parameterise force fields for studying organometallic halide perovskites, with some success at reproducing solid-state properties. However, a force field that can accurately describe dissolution and crystallisation is still lacking.
In this work, we compare existing non-polarizable force fields developed to study the solid or solution phases of organometallic halide perovskites with the AMOEBA polarizable force field. The aim is to test whether computationally expensive polarizable force fields like AMOEBA offer better transferability between liquid and solid phases, the ultimate goal being the study of pre-critical clusters, nucleation and interfaces of organometallic halide perovskites.
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| Michael Rinaudo | University of Sydney | |
| Dominic Robe | Monash University | YouTube
Brownian Dynamics Simulation of Associating Star Polymer Networks |
| Abstract: The relationship between microscopic structure and mechanical properties is often complex, particularly in the presence of nontrivial molecular architecture. In a few cases, carefully constructed systems allow us to probe this relationship systematically, and even target specific material properties. Here we study solutions of star polymers with reversibly associating functional groups on the dangling ends of the star’s arms. Recent experiments have shown that the linear viscoelastic response of such systems can exhibit a finely-resolved single Maxwell mode of relaxation. This phenomenon can be modelled as an ideal reversible network of molecules, each singly associated with each of its neighbours. The concentration of associated stars and the time scale for their dissociation determine the instantaneous shear modulus and relaxation time of the solution. We study star polymer solutions using the GPU-accelerated multi-particle simulation toolkit HOOMD-Blue combined with an O(N) algorithm for Brownian Dynamics with hydrodynamic interactions. Our simulations investigate the dynamics of star polymer gels and universal properties of single stars such as swelling and diffusivity. The storage and loss moduli of networks of stars are computed as functions of association strength and concentration and compared with results from experiment. Finally, with detailed molecular trajectories in hand, we test the ideal network model of relaxation for these associative star polymers, and examine the dependence of network topology and relaxation mechanisms on increasing strain rate and amplitude.
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| Souvik Sadhukhan | Tata Institute of Fundamental Research, Hyderabad, India,500046 | YouTube
Glassy Dynamics in Confluent Biological Tissue |
| Abstract: Hallmarks of glassy dynamics in a confluent biological tissue is important for wound healing, morphogenesis, tumor progression etc. We have developed a theoretical framework for glassiness in such systems through a combination of numerical study of cellular Potts model (CPM) and an analytical study based on random first order transition (RFOT) theory for a confluent system. In this talk, I will present our extended RFOT theory, some of the distinct glassy properties of a confluent system, and a comparison of our theoretical predictions with simulations as well as existing experimental results.
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| Sina Safaei | University of Auckland | |
| Aritra Santra | Monash University | |
| Gerd Schröder-Turk | Murdoch University | Hyper uniform disordered states in voronoi liquid tessellation models at zero and finite temperatures (invited talk) |
| Zakiya Shireen | University of Melbourne | |
| Mirella Simoes Santos | University of Queensland | |
| Gang Sun | | |
| Natalie Thamwattana | University of Newcastle | Continuum approach for modelling nanostructures (invited talk) |
| Abstract: This talk is divided into two parts. First, we look at a continuum approach using the Lennard-Jones potential to determine the interaction energy between two nanostructures. Here, we consider models for the interactions involving homogeneous and heterogeneous molecules. In the second part, we use calculus of variations to determine the minimum energy configurations of grafolds and graphene wrinkles.
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| Billy Todd | Swinburne University of Technology | |
| Alfred Uhlherr | | |
| Rahil Valani | Monash University | YouTube
Stop-and-go motion of superwalking droplets |
| Abstract: Vertically vibrating a liquid bath with two frequencies $f$ and $f/2$ with a relative phase difference $\Delta\phi_0$ can give rise to self-propelled superwalking droplets on the liquid surface. We have numerically investigated such superwalking droplets with the two driving frequencies slightly detuned resulting in the phase difference $\Delta\phi(t)$ varying linearly with time. Our model predicts the emergence of stop-and-go motion of droplets, consistent with the experimental observations [Valani et~al. Phys.~Rev.~Lett. {\bf 123}, 024503 (2019)]. Our simulations in the parameter space spanned by the droplet size and the rate of traversal of the phase difference uncover three different types of locomotion: back-and-forth, forth-and-forth, and irregular stop-and-go motion. Our findings lay a foundation for further studies of dynamically driven droplets, whereby the droplet's motion may be guided by engineering arbitrary time-dependent functions $\Delta\phi(t)$.
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| Sleeba Varghese | Swinburne University of Technology | |
| Asaph Widmer-Cooper | University of Sydney | TBA (invited talk) |
| Marltan Wilson | University of Adelaide | |
| Jared Wood | University of Sydney | |
| Junting Xiang | University of Melbourne | |
| Christian Zuluaga Bedoya | University of Queensland | |