Department of Physics, Islamic Azad University, Central Tehran Branch, PO. Code 14168-94351, Iran.
In this paper, we study the Casimir effect of a scalar field with Dirichlet boundary condition in some certain topologies. By numerical analysis we show that Casimir energy is a shape-dependent quantity. We also obtain the phase transition in different topologies in which the Casimir force changes from attractive to repulsive or vice versa. eararqr