Relativistic LCGTO-FF calculations of quantum-size effects in plutonium films

摘要

Linear combinations of Gaussian-type orbital-fitting function (LCGTO-FF) calculations have been used to study quantum size effects in the work function and surface energy of unrelaxed ultra-thin (001) films of fcc (delta) plutonium (Pu), up to five layers thick. Relativistic effects are included in the calculations using the second-order Douglas-Kroll-Hess transformation, at the fully- and scalar relativistic levels of approximation, i.e., with and without spin-orbit coupling terms included. In both approximations, the surface energy is found to be rapidly convergent, while the work function exhibits a significant quantum size effect up to the largest thickness considered. The (001) surface energies predicted are notably larger than the (111) surface energies found in similar calculations. The predicted work functions for the (001) and (111) surfaces agree to within the computational uncertainty due to the residual quantum size effect. (c) 2005 Wiley Periodicals, Inc.