Periodic boundary conditions

Vampire is capable of simulating pseudo bulk materials through the application of periodic boundary conditions. Here the interactions of the spins at the edge of the system are replicated to remove edge effects. In addition the periodicity in x,y and z directions can be controlled explicitly, to simulate for example a pseudo-infinite thin film by replication in x and y directions only. Periodic boundary conditions can be specified in the input file using the keywords


Periodic boundaries are only applied to spins at the edge of the total system size, and so if the system is cut into a 3D shape (such as a sphere) less than the system size then the periodic boundaries will have no effect.


While the exchange interactions are periodic the demagnetizing fields are finite and so edge effects will be apparent. It is planned to add periodic demagnetizing fields as a separate option in future.