The instable zone of an interstitial atom is investigated in the vicinity of the impurity‐vacancy complex in α‐iron by the molecular dynamics method. A wide range of substitutive impurity atoms distinguished by the relaxation volume is considered. The effect is assessed of impurities on the Frenkel pair recombination region size. The mutual positions of interstitial atoms and substitutive impurities with a negative relaxation volume, at which the spontaneous displacement of the latter from lattice points is accomplished into one of the stable interstitial positions, are determined. The recombination of mixed dumbbell and other interstitial configurations of the impurity with vacancies is considered.