Phase and structural transformations in a molecular dynamics model of iron under ultrafast heating and cooling

It is shown that a system of classical particles considered in a molecular dynamics model with Pak-Doyama pairwise interatomic potential adequately describes not only the various structural states of iron (melt, bcc crystal, metal glass) but also the complex self-organization processes occurring in first- and second-order phase transitions (crystallization and vitrification, respectively). When the temperature is varied at a constant rate of 6.6 x 10(11) K/s, crystallization sets in from both the amorphous and the liquid state; at a rate of 1.9 x 10(12) K/s, crystallization is observed only in the amorphous state; and when heated at a rate of 4.4 x 10(12) K/s, the model amorphous iron transfers to the liquid state without crystallization. The energy of homogeneous formation of a crystal nucleus in the bulk of the amorphous phase of iron is calculated to be similar to0.71 eV under the assumption that there is a spectrum of activation energies. (C) 2001 MAIK "Nauka/Interperiodica".