Subcascade formation in 200 keV Pt cascades

K. Nordlundš˛ and R. S. Averbackš

š Materials Research Laboratory, University of Illinois at Urbana-Champaign Urbana, IL 61801, USA

˛ Accelerator Laboratory, University of Helsinki, P.O. BOX 43, FIN-00014 Helsinki, Finland

(Decemeber 17, 1997)

This material is auxiliary material to the publication "Role of electron-phonon coupling on collision cascade development in Ni, Pd and Pt", by K. Nordlund, L. Wei, Y. Zhong and R. S. Averback (submitted for publication in Phys. Rev. B). A preliminary preprint is available here. Related publications can be found in my publication database.

200 keV Pt

The above figures show the liquid atoms in two distinct collision cascades induced by a 200 keV self-recoil in bulk Pt, at about 0.4 ps after the initiation of the recoil.

To obtain an animation of the cascades in any of the materials, click on either the figure itself or the 2D or 3D buttons to obtain a 2-dimensional or 3-dimensional view. Each dot shown is an energetic atom; the colors are proportional to the depth scale in the 2D figures, and proportional to the energy in the 3D ones, with the red atoms being hottest at the given time. In the 3D figures, also the atoms size is proportional to the kinetic energy. (To view the animations, you need a web browser or browser plugin which can show GIF animations. Recent versions of Netscape or Microsoft Internet Explorer should be able to do this).

Note how the two cascades are quite different in shape: one is roughly spherical (except for the long replacement collision sequence peak emanating to the top left), whereas the other is elongated and essentially consists of two separate liquid pockets. This is typical at the energy close to the subcascade breakdown threshold: some cascades are still continuous, while others are not. This has a large effect on the mixing: since the continuous liquid cools down much slower, the atoms have more time to diffuse in the liquid zone, resulting in a much larger mixing. In the two cases shown, the continuous even turns out to have a mixing twice as large as the other one !

From the animations, you will also see the pressure/heat wave emanating from the cascade as platelets of dots surrounding the liquid core. These atoms are of course not really liquid. Rather, due to the intense heat in the center of the 200 keV cascade the kinetic energy of the atoms in the heat wave actually can exceeds the melting temperature, making them visible in the plots.