All-electron LCGTO calculations for uranium dioxide

The linear combinations of Gaussian-type orbitals-fitting function (LCGTO-F F) technique is used to study the zero-pressure properties of crystalline u ranium dioxide, a prototypical heavy element bearing Mott-Hubbard insulator . The effects of several common approximations are examined: (1) scalar vs, full relativity; (2) paramagnetic vs. spin polarized; and (3) local densit y approximation (LDA) vs, generalized-gradient approximation (GGA). UO2 is incorrectly predicted to be a metal for all approximations considered here, as expected for a Mott-Hubbard insulator. The lattice constant and bulk mo dulus obtained using the highest level approximations are, however, in exce llent agreement with experiment. This suggests that the strong correlation effects that are generally believed to produce the observed band gap do not have a significant impact on the binding properties of UO2, contrary to th e results of recent LDA+U calculations. (C) 2000 John Wiley & Sons, Inc.