6533b7d8fe1ef96bd126a25e

RESEARCH PRODUCT

A predictive model for the electronic stopping force for molecular dynamic simulation (I)

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Abstract We have examined a predictive model for the electronic stopping force (dE/dx)e to be used in the classical molecular dynamic (MD) simulation. The essential term (dE/dx)proton of (dE/dx)e is based on the Lindhard–Winther theory, while the effective charge follows the Brandt–Kitagawa model. The (dE/dx)proton term is expressed by the electron local density ρ(r) defined by the Muffin-tin model and the Hartree–Fock–Slater approximation. This model had been proposed to explain the impact-parameter dependence of (dE/dx)e for channeling ions passing through a semiconductor. Here the energy dependence of the averaged 〈dE/dx〉e after thin-film transmission was examined, where the electron–phonon interaction can be ignored in the computation. The present work uses a nitrogen (14N) beam passing through a diamond with energies from 10 to 100 keV, which is fully included in the region. Because of the channeling components in the crystalline target, the calculated data 〈dE/dx〉e was 10% smaller than that of measured values in an amorphous target. The exponent of the energy dependence of 〈dE/dx〉e (∝ E0.473) was a little gentler than that assumed in conventional models as (dE/dx)e (∝ E0.5). We have confirmed that this predictive model without a free parameter will be useful in a new system, even for a MD simulation that will take into account the electron–phonon interaction for a non-metallic target.