It was found that a new type of defect structure, on the {001}-type planes, was created by deuteron bombardment. High-resolution electron microscopic observations revealed that the defect was of interstitial type, with a double period of a {001} plane in the <110> projection. The structure was formally constructed by connecting two {100} 2 x 1 surfaces that were rotated by 90 with respect to each other. No dangling bonds were involved.

S.Muto, S.Takeda: Philosophical Magazine Letters, 1995, 72[2], 99-104