Product Code Database
Patchy particles are micron- or nanoscale colloidal particles that are anisotropically patterned, either by modification of the particle surface chemistry ("enthalpic patches"), through particle shape ("entropic patches"), or both. The particles have a repulsive core and highly interactive surfaces that allow for this assembly. The placement of these patches on the surface of a particle promotes bonding with patches on other particles. Patchy particles are used as a shorthand for modelling anisotropic colloids, proteins and water and for designing approaches to nanoparticle synthesis. Patchy particles range in valency from two (Janus particles) or higher. Patchy particles of valency three or more experience liquid-liquid phase separation. Some phase diagrams of patchy particles do not follow the law of rectilinear diameters. and feature reentrant nucleation rates.
Other simulations involve biased Monte Carlo moves. One type is aggregation volume-bias moves. It consists of 2 moves; the first tries to form bond between two previously unbonded particles, the second tries to break an existing bond by separation. Aggregation volume-bias moves reflects the following procedure: two particles are chosen, I and J, which are not neighboring particles, particle J is moved inside the bonding volume of particle I. This process is carried out uniformly. Another aggregation volume-bias move follows a method of randomly choosing a particle J that is bonded to I. Particle J is then moved outside the bonding volume of particle I, resulting in the two particles no longer being bonded. A third type of aggregation volume-bias move takes a particle I bonded to particle J and inserts it into a third particle.
Grand canonical ensemble is improved by aggregation volume-bias moves. When aggregation volume-bias moves are applied, the rate of monomer formation and depletion in enhanced and the grand-canonical ensemble moves increase.
A second biased Monte Carlo simulation is virtual move Monte Carlo. This is a cluster move algorithm. It was made to improve relaxation times in strongly interacting, low density systems and to better approximate diffusive dynamics in the system. This simulation is good for self-assembling and polymeric systems that can find natural moves that relax the system.
Tetrahedron faceted spheres are targeted by beginning with simple spheres. In coordination with the faces of a tetrahedron, the sphere is sliced at four equal facets. Monte Carlo simulations were performed to determine different forms of α, the faceting amount. The particular faceting amount determines the lattice that assembles. Simple cubic lattices are achieved in a similar way by slicing cubic facets into spheres. This allows for the assembly of simple cubic lattices. A bcc crystal is achieved by faceting a sphere octahedrally.
The faceting amount, α, is used in the emergent valence self-assembly to determine what crystal structure will form. A perfect sphere is set as α=0. The shape that is faceted to the sphere is defined at α=1. By fluctuating the faceting amount between α=0 and α=1, the lattice can change. Changes include effects on self-assembly, packing structure, amount of coordination of the faceting patch to the sphere, shape of the faceting patch, type of crystal lattice formed, and the strength of the entropic patch.
|
|
