A structural model was proposed for the type-C defect on (001). It was based upon the assumption that the type-C defect arose from the removal of only 1 atom from the second layer and not from the removal of 2 atoms from the surface. The optimized structure that was deduced from first-principles calculations reproduced scanning tunnelling microscopic images under both negative and positive sample biases.

T.Uda, K.Terakura: Physical Review B, 1996, 53[11], 6999-7001