Symmetry-broken self-interstitial defects in chromium, molybdenum, and tungsten

Since the nineteen-seventies, it was believed that the results of Huang x-ray diffuse scattering from radiation defects proved that a self-interstitial atom (SIA) defect in Mo adopted a 110 dumbbell configuration. However, resistivity recovery experiments performed using the same irradiated materials suggested a different, highly mobile, 111 SIA defect structure. Using density functional theory calculations, the authors have discovered that an SIA adopts a symmetry-broken 11ξ configuration in chromium, molybdenum and tungsten, where ξ is an irrational number. A 11ξ defect migrates on average one-dimensionally through a sequence of three-dimensional nonplanar transitions, well correlated with the observed defect migration temperatures. Direct simulations of Huang diffuse scattering patterns from 11ξ defect structures agree with observations, fully resolving the problem of the structure of defects in Mo and similar metals.