There are some quite general and quite unex- pected features of the high temperature behaviour of metals being reviewed by Ya. Kraftmakher. These are the discrepancy between the estimated number of point de fects, determined by equilibrium and quenching experi ments, the discrepancy between a number of point de- fects, estimated by high temperature dilatometric mea- surements and heat capacity ones, as well as the pecu- liarities in changing the selfdiffusivity mechanisms at high temperatures. The mechanisms of these phenomena had been analysed, but some new qualitative and semi- quantitative approaches are here suggested for explain- ing the named paradoxes as the basis of a model of un- stable pairs vacancy-atom at interstice, being the third type of equilibrium point defects in solids, in addition to Frenkel 's and Shottkv 's defects.
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