Critical Point of Ising Films with Different Growth Directions

The critical temperature T_c of a spin-1/2 Ising film of cubic structures is calculated by the variational cumulant expansion method for three directions of growth. The results from different growth directions are analysed and compared with each other. In the present model, the T_c values depend largely on the number of nearest neighbors in a monolayer for films with the same number of monolayers but grown in different directions. For sc, bcc and fcc structures, the highest T_c is found along the (100), (110), and (111) direction, respectively.