Calculation of mean excitation energy and stopping cross section in the orbital local plasma approximation.

Abstract

Extension of the kinetic theory of stopping, in the Oddershede-Sabin (OS) (At. Data Nucl. Data Tables 31, 275 (1984)) orbitally decomposed form, from gas phase to films and crystals generates the need for orbital mean excitation energies calculated within the local-spin-density approximation (LSDA) to density-functional theory (DFT), the preeminent theoretical model for such extended systems. In LSDA, the orbitals and orbital energies used in the construction of the electron density {rho} have no standing for estimation or calculation of excitation energies. As an alternative we propose an orbital density generalization of the local plasma approximation (LPA) of Lindhard and Scharff (K. Dan. Vidensk. Selsk. Mat. Fys. Medd. 27, No. 15 (1953)) that we test by calculation of mean excitation energies {ital I}{sub {ital k}} for each atomic orbital {ital k} within the LSDA for all atoms with {ital Z}{lt}37. Stopping cross sections for a representative sample (about half) of these elements have been calculated using these {ital I}{sub {ital k}} values. The results do not differ substantially from those of OS (who used {ital I}{sub {ital k}} values from Dehmer, Inokuti, and Saxon (Phys. Rev. A 12, 102 (1975)); Inokuti, Baer, and Dehmer ({ital ibid}. 17, 1229 (1978)); Inokuti, Dehmer,more » Baer, and Hanson ({ital ibid}. 23, 95 (1981))), with the discrepancy generally less than 15%.« less