MESODYNDATASHEET

MesoDyn is a dynamic simulation method for studying thelong length and time behavior of complex fluid systems,
including polymer melts and blends. It has gained wide
respect in literature and commercial circles with scientificallyastute algorithms aimed at elucidating industrially important
mesoscale structure and kinetics. Such structures are found tocritically affect the bulk properties of a material and are often
frozen in by processing, where timescales may be of the sameorder as relaxations. The dynamics of the system is describedby a set of so-called functional Langevin equations. In
simple terms, these are diffusion equations in the component
densities which take account of the noise in the system.
By means of numerical inversions, the evolution of thecomponent densities is simulated, starting from an initiallyhomogeneous mixture in a cube of typical size 100-1000 nm
and with periodic boundary conditions.

A flexible client-server architecture means that calculations
can be run on servers located elsewhere on your network.
Additionally, MesoDyn uses MPI to run in parallel and is also
supported for submission to a server through queuing systems.
Results are returned to your PC, where they may be displayed
and analyzed. You can easily produce high quality graphics
of molecular and mesoscopic material structures. Structures,graphs, and other data (such as video clips), produced from
MesoDyn output can be instantly exchanged with other PC
applications.

WHAT DOES MESODYN DO?
MesoDyn takes a coarse-grained description of a complex
fluid and performs time-evolution dynamics of the densityand potential fields of the system. The free energy seeks aminimum which may be achieved by demixing if intermolecularforces are sufficiently disfavored. The coarsegraining of thesystem involves replacing polymer chains by a Gaussian
representation with the same response functions and including
non-ideality of the system via effective external potentials,
the magnitude of which is determined by the Flory-Huggins
interaction parameters of the various binary pairs in thesystem. Electrostatics may be included via the Flory-Huggins
parameter, or may be explicitly included for each bead in thesystem.

The BIOVIA Materials Studio Advantage
MesoDyn is operated from within the BIOVIA Materials
Studio® environment. BIOVIA Materials Studio provides anintegrated user-interface that is easy to use and quick to learn.
BIOVIA Materials Studio Visualizer, the core BIOVIA Materials
Studio product, offers a wide range of model building andvisualization tools that allow you to rapidly construct modelsof the system of interest, calculate the necessary molecularlevel information that is required for the parameterization ofmesoscale simulation, select the MesoDyn module with two
mouse clicks, and run a dynamic simulation of a complex fluid.

Image from a MesoDyn simulation of the phaseseparation of diblock copolymer. The surface links pointat the dividing surface between the two phases. Theentire volume is color-coded by the density of one of theblocks (red at higher density, blue at low density). This
image is a state prior to equilibrium, and the systemultimately evolves to a lamellar phase.

HOW DOES MESODYN WORK?
MesoDyn simulates fluid phases that are homogeneous indensity, but show compositional fluctuations. The structure
and potential energy of the system evolve over time due tochemical potential gradients and Langevin noise. The noise
term is important in escaping local minima on the free energy
surface of the system. The equilibration of the system canbe followed by monitoring the free energy evolution. Orderparameters are also calculated to quantify the degree of phaseseparation.

FEATURES AND CAPABILITIESCalculation tasks• Define up to 10 chemical species• Define up to 10 mesoscale molecules (represented by single
beads or chains of beads with arbitrary connectivity)• Define interaction energies for each pair of species in thesystem, these energies are proportional to the Flory-Huggins
interaction parameter chi and lead to the phase separation ofvarious components• Define temperature, cell composition, cell size, run length,and output frequencies• Include walls or other constraints (where preferential
adsorption of certain species may be included)• Define a specific constraint (such as ordered array of spheres
and wedge-shaped cell)• Shear the system• Perform the free energy integration in potential space only,
speeding up the calculation considerably• Explicitly include charges in the system using a DebyeHuckel approximation for simulation of aqueous systems• Alter the composition at restart, allowing the study of effects
such as titration, solvent evaporation, and shifts in chemicalequilibrium• Restart a simulation from a previous run, resetting theaverages if desired and altering the interactions between
beads to create quite complex scenarios (e.g. to model theeffect of a change in pH or controlled release of drug)

Properties• Phase morphology• Aggregation and coagulation• Effect of confinement on miscibility• Effect of shear on morphology• Concentration profiles• Density histograms• Free energy and entropy evolution• Species potential plots (indicating areas of high and lowenergy)• Compositional order parameters, giving a direct measure ofphase separation
To learn more about BIOVIA Materials Studio,
go to accelrys.com/materials-studio

REFERENCES:
1. J. G. E. M. Fraaije, B. A. C. van Vlimmeren, N. M. Maurits, M. Postma, O. A. Evers, C.Hoffman, P. Altevogt,
and G. Goldbeck-Wood, “The dynamic mean-field density functional method and its application to themesoscopic dynamics of quenched block copolymer melts,” Journal of Chemical Physics, 1997, 106, 4260.
2. N. M. Maurits, A. V. Zvelindovsky, G. J. A. Sevink, B. A. C. van Vlimmeren and J. G. E. M. Fraaije,“Hydrodynamic effects in 3d microphase separation of block copolymers: dynamic mean-field density
functional approach,” Journal of Chemical Physics, 1998, 108, 500.
3. A. V. Zvelindovsky, G. J. A. Sevink, B. A. C. van Vlimmeren, N. M. Maurits and J. G. E. M. Fraaije, “3Dmesoscale dynamics of block copolymers under shear: the dynamic density functional approach,”Phys. Rev. E., 1998, 57, 4699.

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The inclusion of pseudo-dynamic algorithms makes thesimulation much faster, and the direct incorporation ofelectrostatics greatly increases the number of systems thatcan be studied with MesoDyn. The ability to create arbitrary
confinement scenarios (such as arrays of spheres, planar walls,and wedges) makes studies of confined systems particularlyinteresting in BIOVIA Materials Studio. For the first time, theuser has the ability to visualize the constraint in the absence ofthe density fields.