| Steven Carnie | University of Melbourne | Slip sliding away: how a bubble slips along a hydrophilic surface |
| Derek Chan | University of Melbourne and Swinburne University of Technology | Dynamics of aerated powder beds |
| Nathan Clisby | University of Melbourne | |
| Peter Daivis | RMIT University | |
| Matthew Downton | IBM Research | Cell-veto Monte Carlo simulations of liquid water |
| Dave Dunstan | The University of Melbourne | Modelling polymers as elastic spheres in Couette flow |
| Abstract: A model of polymer chains as deformable elastic spherical blobs in flow is presented. The blobs are assumed to compress in simple Couette flow in accord with recent experimental evidence in Macromolecules, 37, 1663 (2004) and JPC Letts, 1, 1912 (2010). The experimentally measured decrease in radius with increasing shear rate is predicted by the model. Furthermore, the model predicts power law exponents for the viscosity-shear rate within the range of measured values for polymer chains. |
| Ian Enting | University of Melbourne | |
| Elmira Fadaei-Azar | None | |
| Dhefaf Faisal | Swinburne University | |
| Kirill Glavatskiy | The University of Queensland | Thermodynamics resistance of the surface of nanoporous membranes |
| Abstract: Nanoporous materials are important in industrial separation, but their application is subject to strong interfacial barriers to the entry and transport of fluids. At certain conditions the fluid inside and outside the nanoporous material can be viewed as a two-phase system, with an interface between them, which poses an excess resistance to matter flow. We show that there exist two kinds of phenomena which influence the interfacial resistance: hydrodynamic effects and thermodynamic effects, which are independent of each other. Here, we investigate the role of the thermodynamic effects in carbon nanotubes (CNTs) and slit pores and compare the associated thermodynmic resistance with that due to hydrodynamic effects traditionally modeled by the established Sampson expression. Using CH4 and CO2 as model fluids, we show that the thermodynamic resistance is especially important for moderate to high pressures, at which the fluid within the CNT or slit pore is in the condensed state. Further, we show that at such pressures the thermodynamic resistance becomes comparable with the internal resistance to fluid transport at length scales typical of membranes used in fuel cells, and of importance in membrane-based separation, and nanofluidics in general |
| Marsel Gokovi | University of Queensland | Structure and Diffusion of Charged, Confined Particles |
| Stephen Hannam | RMIT University | Molecular dynamics calculations of the intermediate scattering functions for a model colloidal fluid with explicit solvent |
| Abstract: Colloidal suspensions are extremely useful model systems for the study of nucleation and vitrification. They show a phase behavior that can be mapped onto a hard-sphere (HS) system, but also exhibits a glass transition [1,2]. The common methods used to study these systems experimentally are dynamic light scattering (DLS) and x-ray photon correlation spectroscopy (XPCS).
As a compliment to light scattering experimental results, Molecular Dynamics (MD) simulation was used to study a model colloidal suspension. We used a model that has been shown to reproduce the structure [3], and approximate dynamics [4], of a real colloidal suspension. The intermediate scattering function (ISF) was calculated over a wide range of concentrations and wavevectors for systems with unimodal and bimodal size distributions.
A multiexponential analysis was performed on the ISF data and it was found that an extra mode appeared in the bimodal system. This exponential mode is linked to the relaxation of composition, and its decay rate was found to decrease to a negligible value at the glass transition, leading to an extremely long-lived metastable state.
[1] P. N. Pusey and W. van Megen, Nature London 320, 340 (1986).
[2] W. van Megen and S. M. Underwood, Nature London 362, 616 (1993).
[3] S. D. W. Hannam, P. J. Daivis and G. Bryant, Molecular Simulation 42, 511 (2016).
[4] S. D. W. Hannam, P. J. Daivis, and G. Bryant, Phys. Rev. E 94, 012619 (2016). |
| Peter Harrowell | University of Sydney | Mechanical Properties of Inhomogeneous Materials: What we Learn from Normal Modes |
| Yuan-Chao Hu | Department of Mechanical and Biomedical Engineering, City University of Hong Kong | Density scaling of glassy dynamics and dynamic heterogeneities in glass-forming liquids |
| Abstract: The discovery of density scaling is an important progress for understanding the dynamic behaviors of supercooled liquids, which has been validated in more than 100 'strongly correlating' systems, like van der Waals liquids and polymers. However, here we found that for a ternary metallic glass-forming liquid, it is not strongly correlating thermodynamically, but its average dynamics, dynamic heterogeneities including the high order dynamic correlation length, and static structure are still well described by density scaling with the same scaling exponent γ. This may indicate that the metallic liquid could be treated as a single-parameter liquid. As an intrinsic material constant stemming from the fundamental interatomic interactions, γ is theoretically predicted from the thermodynamic fluctuations of the potential energy and the virial. Although γ is conventionally understood merely from the repulsive part of the inter-particle potentials, the strong correlation between γ and the Grüneisen parameter up to the accuracy of the Dulong-Petit approximation demonstrates the important roles of anharmonicity and attractive force of the interatomic potential in governing glass transition of metallic glass-formers. To further quantify the effects of attractive interactions on supercooled dynamics and density scaling behaviors, model glass-forming liquids with tunable attractive potentials were simulated. It is found that the dynamics slows down more severely in liquids with strong short-ranged attractive potentials. In addition, the density scaling exponent is distinct from those with weak long-ranged attractive potentials, which further demonstrate the nonperturbative effect of attraction in glass-forming liquids. These findings may shed light on how to understand glass formation from the fundamental interatomic interactions. |
| David Huang | The University of Adelaide | Magnetic fields and morphology in singlet fission and triplet fusion |
| Tom Hunt | IIT | |
| Ravi Jagadeeshan | Monash University | Stretch-relaxation of DNA molecules in semidilute solutions |
| Owen Jepps | Griffith University | |
| Joseph Johnson | University of Melbourne | Approximate Solution to the Boltzmann Equation at Arbitrary Knudsen Number |
| Sanath Kahagalage | School of Mathematics and Statistics, the University of Melbourne | Emergence of cracks along force bottlenecks in a cementitious granular material |
| Sridhar Kannam | IBM Research, Australia | |
| Matthew King | Griffith University | Relaxation in a harmonic potential |
| Daniel Ladiges | The University of Melbourne | |
| Daniel Lester | RMIT | |
| Ruru Li | RMIT University | |
| Alan Mark | University of Queensland | Perturbation approaches for the paramaterization of solvation free energies and the properties of simply liquids |
| Adrian Menzel | RMIT University | Planar Poiseuille Flow of Highly Confined Polymer Solutions |
| Abstract: In this work, we simulate coarse-grained model polymer solutions in highly confined channels both in equilibrium and undergoing Poiseuille flow, using molecular dynamics techniques.
We find that the temperature, velocity, and concentration profiles across the channel vary with flow rate. In particular, increasing the flow rate leads to an increase in the wall-mediated polymer depletion region. We show that for sufficiently large channel-widths a bulk-like flow can be achieved that behaves according to classical continuum equations for velocity and temperature. Despite previous research to the contrary we find that even at thinner channel widths the continuum equations with equilibrium transport coefficients still provide a valid description of the flow. We also find no strain-rate coupling to the thermal conductivity.
Finally, we have also implemented an algorithm to calculate the local pressure tensor across the channel, and have studied the variation of the first normal stresses with position and compared the results with predictions of the first normal stress coefficients from equilibrium molecular dynamics simulations. |
| Ashwin Nandagiri | Monash University, IITBombay (India) | |
| Alex Nunn | The University of Melbourne | |
| Timothy O'Sullivan | University of Melbourne | |
| David Ostler | Swinburne University | Electropumping of water through functionalised carbon nanotubes |
| Abstract: There are many nanotechnology applications that would benefit from being able to effectively pump water through nanotubes, including lab-on-a-chip technologies, drug release and delivery, and desalination. Continuum hydrodynamics analysis and Nonequilibrium Molecular Dynamics (NEMD) simulations have shown that a net positive flow can be generated by applying a rotating electric field to a polar fluid confined to a nanochannel or nanotube when that nanochannel or nanotube has asymmetric hydrodynamic boundary conditions (electropumping). In this presentation we show that sufficient asymmetric boundary conditions can be created for electropumping by functionalising part of carbon nanotube with carboxyl groups. We also demonstrate that the effectiveness of electropumping is related to the degree of functionalisation and nanotube diameter. |
| Mihail Popescu | Max Planck Institute for Intelligent Systems, Dept. Theory of Inhomogeneous Condensed Matter | Chemically active colloids near osmotic-responsive walls with surface-chemistry patterns: from artificial thigmo-taxis to pattern-guided motion |
| Abstract: Chemically active colloids self-generates solute density and hydrodynamic fields, which induce particle motion. Near a hard planar wall chemi-osmotic hydrodynamic flow at the wall is also induced by the solute density originating at the colloid. This wall-response flow couples back to the Janus particle and an interplay with the self-diffusiophoretic motion arises. By using far-field analytical arguments, complemented and crossed-check by exact numerical solutions, we show that an alignment of the symmetry-axis of the particle to the local gradient in surface chemistry of the wall emerges; i.e., these man-made objects exhibit a primitive form of thigmo-taxis (in analogy to micro-organisms sensing the proximity of a physical change in the environment). Furthermore, we predict that through suitable chemical patterning of the wall one can achieve controlled motion of the chemically active Janus particle, e.g., the particle following a chemical stripe or being “docked” at a chemical step. |
| Sebastian Pucilowski | University of Melbourne | |
| Malcolm Ramsay | University of Sydney | The coupling of translational and rotational motion in supercooled molecular liquids |
| Nastaran Rezaee | Swinburne University | |
| Shibu Saw | The University of Sydney | Structure, dynamics and rigidity at the crystal-glass interface |
| Philipp Schoenhoefer | Murdoch University | A Bicontinuous Gyroid Phase in Purely Entropic Self-Assembly of Hard Pears |
| Gerd Schröder-Turk | Murdoch University | Beyond the percolation universality class: the vertex split model for tetravalent lattices |
| Abstract: We propose a statistical model defined on tetravalent three-dimensional lattices in general and the three-dimensional diamond network in particular where the splitting of randomly selected nodes leads to a spatially disordered network, with decreasing degree of connectivity. The terminal state, that is reached when all nodes have been split, is a dense configuration of self-avoiding walks on the diamond network. Starting from the crystallographic diamond network, each of the four-coordinated nodes is replaced with probability p by a pair of two edges, each connecting a pair of the adjacent vertices. For all values $0\leqslant p\leqslant 1$ the network percolates, yet the fraction fp of the system that belongs to a percolating cluster drops sharply at pc = 1 to a finite value $f_{p}^{c}$. This transition is reminiscent of a percolation transition yet with distinct differences to standard percolation behaviour, including a finite mass $f_{p}^{c}\gt 0$ of the percolating clusters at the critical point. Application of finite size scaling approach for standard percolation yields scaling exponents for $p\to {{p}_{c}}$ that are different from the critical exponents of the second-order phase transition of standard percolation models. This transition significantly affects the mechanical properties of linear-elastic realizations (e.g. as custom-fabricated models for artificial bone scaffolds), obtained by replacing edges with solid circular struts to give an effective density phgr. Finite element methods demonstrate that, as a low-density cellular structure, the bulk modulus K shows a cross-over from a compression-dominated behaviour, $K(\phi )\propto {{\phi }^{\kappa }}$ with $\kappa \approx 1$, at p = 0 to a bending-dominated behaviour with $\kappa \approx 2$ at p = 1. |
| Naijian Shen | University of Melbourne | |
| Igor Shvab | Newcastle University, UK | Kinetic Monte Carlo simulations of nanoparticle precipitation: application to cement hydration |
| Abstract: There is a great technological interest in engineering the evolution of the sub-micrometre texture and properties of cementitious materials. These nanoscale features control largely the degradation process, e.g. the effect of nanopore water on drying shrinkage and creep. The large timescales of cement hydration and ageing however challenge all the current nanoscale simulations based on dynamics. Here we propose new approach based on kinetics, which considers the formation and aggregation of nanoparticles representing the cement hydrates. Differently from the existing simulations, the rate of nanoparticle formation is not imposed heuristically but is obtained rigorously from Transition State Theory and information at the molecular scale. The new rates account for the chemical reactions that govern the precipitation of the hydration product and for the mechanical interactions between nanoparticles. This provides a new starting point to quantify how the mix design variables impact the microstructure and properties of cement hydrates over large timescales. Kinetic Monte Carlo simulations based on the new theory, capture well the rate of early hydration and show the effects of solution chemistry and cement surface defects on the hydration rate and the morphology of the hydration product.
This is joint work with Enrico Masoero. |
| Anthony Stickland | The University of Melbourne | Inter-particle Friction and Bulk Rheology of Suspensions |
| Qiang Sun | University of Melbourne | |
| Billy Todd | Swinburne University of Technology | |
| Alfred Uhlherr | '- | |
| Maryna Vlasiuk | Centre for Molecular Simulation, Swinburne University of Technology | Molecular simulation of the thermodynamic, structural and vapour-liquid coexistence properties of neon |
| Abstract: Maryna Vlasiuk, Federico Frascoli, Richard J. Sadus
Our studies of liquid neon are extended to include an additional intermolecular potential and an alternative computational technique.A recent ab initio potential for neon by Hellmann Bich and Vogel (HBV) [1, 2] has been developed using a high level of theoretical detail. Its analytical representation has been chosen with care and incorporates damping functions for each of the multipole expansion terms. This analytical function is used in Monte Carlo simulations in canonical and Gibbs ensemble [3] to calculate thermodynamic, structural and phase equilibrium properties.Our work presents a substantial number of properties, calculated using the HBV potential model using Lustig's formalism [4]. We seek to compare the behaviour of the HBV potential to the empirical Barker-Fisher-Watts [5] potential, which predicts neon's properties with a notable level of accuracy.
The moderate quantum behaviour of liquid neon is accounted for by the Feynman-Hibbs semi-classical potential [6]. Additionally, path integral Monte Carlo simulations [7] are performed to calculate isochoric hear capacity and structural properties of liquid neon.
Our study demonstrates that the Feynman-Hibbs version of the HBV potential predicts many thermodynamic properties more accurately than other potentials of intermolecular interactions.
References
[1] R. Hellmann, E. Bich, et al. Ab initio potential energy curve for the neon atom pair and thermophysical properties of the dilute neon gas. i. neon-neon interatomic potential and rovibrational spectra. Mol. Phys., 106:133, 2008.
[2] E. Bich, R. Hellmann, et al. Ab initio potential energy curve for the neon atom pair and thermophysical properties for the dilute neon gas. ii. thermophysical properties for low-density neon. Mol. Phys., 106:813, 2008.
[3] R. J. Sadus. Molecular Simulation of Fluids: Theory, Algorithms, and Object-orientation. Elsevier, Amsterdam, 1999.
[4] R. Lustig. Mol. Sim., 37(6):457–465, 2011.
[5] J. A. Barker, R. A. Fisher, et al. Mol. Phys., 21:657, 1971.
[6] R. P. Feynman and A. R. Hibbs. Quantum Mechanics and Path Integrals. McGraw-Hill: New York, 1965.
[7] M. E. Tuckerman. Statistical Mechanics: Theory and Molecular Simulation. Oxford University Press, Oxford, 2010. |
| Bill van Megen | RMIT | |
| Joost van der Linden | University of Melbourne | Characterising conduction phenomena in granular, porous media |
| Abstract: A perennial challenge for the characterisation and modelling of fluid flow and heat flow phenomena in granular, porous media is that the internal connectivity of, and interactions between, the pores and the particles exhibit hallmarks of complexity. Multi-scale and nonlinear interactions lead to a plethora of patterns at the mesoscale. In this project, a coherent, data-driven framework is developed to combine micro-computerised tomography, discrete-element modelling and finite-element modelling with two techniques tailored specifically towards uncovering patterns in complex systems: complex networks and machine learning. |