2012 Volume 53 Issue 9 Pages 1571-1577
Theoretical framework of the Cluster Variation Method (CVM) is extended in two directions. One is the construction of a supercell in which the basic clusters are aligned in two dimensional directions. The other one is the introduction of the atomic displacement in the flexible lattice. These extensions of the conventional CVM enable us to calculate a core structure of two parallel superpartial dislocations in B2 ordered phase at finite temperatures. It is shown that a large stacking fault is formed inside the two superpartial dislocations at lower temperatures, while the stacking fault appears outside the superpartial dislocations at higher temperatures.