The most recent observations of dynamical time-dependent fluctuating behaviour of mesoscopic radiation defects in body-centred cubic metals had highlighted the need to develop adequate quantitative models for the structural stability of defects in the mesoscopic limit where defects were accessible to direct in situ electron microscope imaging. In pursuit of this objective, several types of mesoscopic vacancy and interstitial defects in iron and tungsten were investigated and compared by simulating them using recently developed many-body interatomic potentials. It was shown that the mesoscopic vacancy dislocation loops observed in ion-irradiated materials are, without exception, metastable with respect to the transformation into spherical voids, but that the rate of this transformation and even the specific type of the transformation mechanism depended upon the defect size and the properties of the material.

Structure and Metastability of Mesoscopic Vacancy and Interstitial Loop Defects in Iron and Tungsten. M.R.Gilbert, S.L.Dudarev, P.M.Derlet, D.G.Pettifor: Journal of Physics - Condensed Matter, 2008, 20[34], 345214 (10pp)