Calculations of positron lifetimes in a jog and vacancies on an edge-dislocation line in Fe

Behaviour of vacancies in dilute Fe–Re alloys: a positron annihilation study

“…At low temperatures, the obtained s mean values suggest that positrons ''see'' mainly vacancies associated with edge dislocations [13]. The expected mean lifetime of a positron trapped in the vacancy associated with edge dislocation is about 140-150 ps [15]. Taking the above into account, one can say that during the coldrolling process of previously annealed samples, a large number of vacancies and dislocations are generated.…”

“…The calculated lifetimes, using Finnis-Sinclair N-body potential, of a positron trapped in vacancy clusters consisting of two and three vacancies associated with edge dislocations are 157 and 167 ps, respectively [18]. Taking into account that attractive interaction energy between vacancy and edge dislocation is much greater than between vacancy and Re impurity [11,15], the first explanation seems rather unlikely. Moreover, a more detailed spectra analysis using two-state trapping model reveals that the longer positron annihilation lifetime s 2 increases with T. This result also favours creation of vacancy clusters associated with edge dislocations over formation of v-Re pairs.…”

“…According to the first one, the vacancies are released from the edge dislocations and form v-Re pairs [17]. The expected lifetime of a positron trapped in a vacancy formed by a v-Re pair is much higher than for a positron trapped in a vacancy associated with edge dislocations [13,15]. The second model is based upon possible diffusion of vacancies along edge dislocations, which could lead to forming vacancy clusters associated with edge dislocations.…”

“…A trapped positron is easily seen by PALS, as it lives longer than that being in the bulk and encounters bigger electron density. For example, the estimated experimental lifetime s b of a positron in a defectfree a-Fe crystal is not greater than about 110 ps (106 ps [14], 110 ps [15]), while the annihilation lifetime s v of positron in a vacancy in a-Fe is 175 ps [15].…”

Dislocation driven chromium precipitation in Fe-9Cr binary alloy: a positron lifetime study

“…Nature of positron trapping in dislocation containing samples is a subject still evoking continued interest [24][25][26][27] . We have calculated positron lifetime for various defect configurations relevant to the present study and Table I lists our computed lifetimes along with other computed and experimental lifetimes available from earlier reports [26][27][28][29][30] . More details of computed positron lifetimes at the dislocation and Fe-Cr interfacial configurations will be discussed elsewhere 31 .…”