Liquid crystals are phases of matter that are both fluid but have structure. This is possible due to the shape of liquid crystal molecules, which tend to be long and thin. In this simulation, molecules of different shapes, and different amounts of heat energy are simulated.
In the case of long thin molecules with aspect ratio of 10 to 1, there is clear nematic and smectic ordering going on. There also appears to be anisotropic flow.
Molecules with a smaller aspect ratio did not show as striking liquid crystal like ordering.
When molecules were modeled with a rectangular collider with a small aspect ratio, as is seen in one segment of this video, they show a tendency to form regular square arrays.
Spherical colliders as expected show no liquid crystalline ordering or director.
This is just a toy model built in Unity, and it has some clear limitations:
1) there are no attractive forces between molecules
2) molecules are rigid
3) the simulation is only in 2 dimensions
4) the "heat" simulation was done by simply giving each of the molecules a random impulse at regular intervals, which is very unrealistic.
5) the physics of collisions are not likely to be similar to real molecular collisions, as I just used Unity's RigidBody class for physics, and for example, they are not energy conserving.
None the less, the results are quite nice to look at.
Related: The video below shows a static representation of a cholesteric liquid crystal structure.