2 1 O ct 1 99 9 Charge ordering , phase separation and charge pairing in layered 3 D systems

The processes of Coulomb gas ordering in 3D layered system are studied by means of Brownian dynamics approach. It is found that at different densities of the carriers the 3D lattice of charges as well as new specific structures are possible in the system. In particular, at some small density the particles inside the layers can associate into droplets that collectively repulse between neighbouring layers. These droplets possess local stripe structure which orders spontaneously along arbitrary chosen direction. At higher densities a specific ordering of the charges into the tetragonal-like or hexagonal-like structures is observed visually and described numerically. Specific " pairing " of the charges from different layers plays an essential role in formation of all above structures. It is essentially many-body effect in 3D system which can be a reason for unusual properties of layered crystals.