The cluster representation matrices have already been successfully used to
enumerate close-packed vacancy clusters in all single-lattice crystals [I, 2]. Point
defect clusters in double-lattice crystals may have identical geometry but are distinct
due to unique atomic postions enclosing them. The method of representation
matrices is extended to make it applicable to represent and enumerate the point defect
clusters in multi-lattice crystals as well. A computational procedure based on family
representation matrices is developed and applied to the hexagonal close-packed