Monte Carlo Range Calculations for a Thomas-Fermi Potential

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Abstract
Our earlier Monte Carlo calculations of the ranges of atoms having energies from 1 to 100 keV, slowing down in a random solid through binary elastic collisions, have been extended by using a Thomas-Fermi potential to represent the interaction between the moving atom and a lattice atom. The screening radius of the potential is that derived by Firsov. The calculations have been made for a wide variety of target-to-projectile mass ratios. Except for the highest energies, the calculated ranges are considerably shorter than those found previously using the exponentially screened Coulomb potential. Most of the experimental range data lie between the range curves calculated for these two potentials, although the Thomas-Fermi potential gives somewhat better over-all agreement. The shapes of the calculated range distributions give close agreement with those found by experiment in amorphous solids. Average ranges calculated by integrating the reciprocal of the stopping power agree fairly well with these Monte Carlo calculations, especially when the mass of the slowing-down atom is large compared to that of a lattice atom.