Combined model of the material excitation and relaxation in swift heavy ion tracks

Recrystallization as the governing mechanism of ion track formation

“…Indeed, complete and fast track recrystallization is observed in MgO having a “simple” lattice structure with the smallest number of the peaks in the pair correlation function. A similar picture was observed in MD modeling of LiF and NaCl exhibiting no continuous tracks 33 . But large amorphous tracks are detected in YAG with the most “complex” lattice structure (the largest number of peaks).…”

Effect of valence holes on swift heavy ion track formation in Al2O3

“…MD tracing of atoms enables us to obtain the transient lattice DSF and, thus, realistic cross sections of the electron-lattice energy exchange in a relaxing SHI track. The same MD also models the lattice relaxation and spatial dissipation of the excess energy of the atoms after cooling of the electron ensemble [7,8]. The characteristic time of cooling of delocalized electrons in a SHI track due to their spatial spreading is shorter than the time of thermalization of the nonequilibrium lattice [13].…”

“…The electron subsystem cools down quickly due to the diffusion of electrons from the track core (< 100 fs). This time is usually shorter than the characteristic time of atomic vibrations [7,8], which is much shorter than a time needed for any significant changes in the structure or the dynamical properties of the material. Taking this into account, we neglect in this version of the model changes in the lattice DSF during this time and the same DSF is used in Eq.…”

“…Strong electronic excitations may transiently change the interatomic potential. Acting sufficiently long time (a few hundred femtoseconds) such potential changes can result in nonthermal melting effects [7,[29][30][31]. This change of the potential can be also treated as an effect of valence holes.…”

“…The presented microscopic multiscale model describes the kinetics of excitation of a dielectric in a SHI track up to picoseconds after the projectile passage. It consists of three different approaches combined together [7,8]. At the first stage, up to tens of femtoseconds after the projectile passage, a Monte Carlo (MC) [9][10][11] model is applied to simulate initial excitations of the electron subsystem by an SHI as well as further kinetics of fast electrons appearing due to ionization.…”