2D crystal

Formation of Crystal

a java simulation by Xiao-Gang Wen

"Temp" is the temperature that control the strength of thermal fluctuations of the particles. "+Temp/-Temp" buttons adjust the temperature.
"+N/-N" changes the number of the particles.
"Restart" button restarts the simulation.
"In/Out" buttons zoom-in or zoom-out.
"+Spd/-Spd" buttons control the speed. Simulation is more accurate at small speeds.

Explanation

This program simulates the motion of interacting particles. The interaction between two particles is repulsive at small separations and attractive at large separations. The moving particle also experience an additional friction force. So, as time evolves, the particles will settle into a crystal configuration that (locally) minimizes the total potential energy, if the temperature is zero.
As you raise the temperature, you will see the melting of the crystal.
Changing the number of particles and pressing the "Restart" button allow you to obtain different configurations. All those configurations break some symmetries. You may try to figure out what symmetry is broken and what symmetry is unbroken.