Atomistic simulation of the interaction of slow protons with an iron surface

Abstract

Summary. --We have studied the dynamical behaviour of low-energy protons (1.0 eV ~< Ein < 50 eV) interacting with a Fe {100} surface at T = 300 K, by means of molecular-dynamics simulations. The inelastic energy losses have been taken into account by means of a friction term proportional to the projectile velocity and depending on the instantaneous local electronic density experienced by the projectile. For a given incident energy and irradiation geometry, we have estimated the particle and energy reflection coefficients and obtained a detailed evaluation of the different contributions (elastic and inelastic) to the energy loss of the reflected particles.PACS 61.80 -Radiation damage and other structural irradiation effects. -Introduction.The behaviour of hydrogen atoms and ions on metal surfaces is of utmost importance in several fundamental areas of material science. As an example, one can quote the problem of gas permeation of structural materials of the first wall of controlled-fusion devices, where particles of the cold plasma edges, escaping from magnetic confinement, impinge on the wall with a kinetic energy in the typical range 0.1-100 eV [1]. The presence of gas atoms in the bulk of these materials is the main cause of embrittlement and swelling phenomena.Few experimental data are available on the interaction of low-energy hydrogen ions with metal surfaces. Numerical simulations by means of widespread computer codes based on the binary collision approximation (like MARLOWE [2]) are not practicable, without ad hoc modifications, since the above-mentioned approximation breaks down in that energy range.Molecular dynamics (MD) seems to be, in this sense, a unique tool for investigating the microscopic surface structure and the dynamics of hydrogen on the surface. In this work we have performed a computer experiment, analogous to that of ref.[3], devoted to the interaction of helium ions with a nickel surface: it consists in studying the behaviour of a big number of protons thrown on an iron surface, one at a time, and estimating both the main thermodynamic and structural parameters of the 1263

Microscopy and Microanalysis of Hematite Precipitates from the Zinc Industry

“…In current industrial practice, both the jarosite and hematite residues are sent to disposal sites. Although the jarosite process is more commonly used, jarosite precipitates are voluminous and require an extensive containment area [3]. The hematite process is more costly, but produces a compact, more stable material for disposal; furthermore, hematite precipitates have some market potential [4].…”