Structural phase transition of di-block polyampholyte

We have performed both conventional canonical molecular dynamics (MD) and multicanonical MD (MMD) simulations for a single di-block polyampholyte in vacuum to investigate possible structural phase transitions. The conventional canonical MD simulation for temperature T* > 0.05 gives reliable results, since these are independent of the initial conformation. The MMD simulation results for temperature T* > 0.05 are in good agreement with those of the conventional canonical MD simulation. Glassy-like states are obtained when quenched into temperatures below T* similar to 0.05 with a straight chain structure as an initial conformation. On the other hand a spherical double helical structure is obtained when the temperature is gradually lowered to T* similar to 0.01. Also we find a stretched double helical structure at T* similar to 0.01 which changes to the spherical double helical structure by annealing and quenching.