Structural properties of crystalline uranium from linear combination of Gaussian-type orbitals calculations

Scalar-relativistic linear combinations of Gaussian-type orbitals-fitting function (LCGTO-FF) calculations, using the local density approximation (LDA) and generalized gradient approximation (GGA) to density functional theory, were used to determine the atomic volumes, bulk moduli, and relative stabilities of uranium in the fcc, bcc, and α-U (orthorhombic) phases. The α-U phase is found to be the most stable, in agreement with experiment. The LDA yields an atomic volume that is about 7% smaller than experiment, while the GGA produces near perfect agreement with experiment. The numerical stability of the LCGTO-FF results is tested by comparison with a similar series of scalar-relativistic calculations using the full-potential linearized augmented plane-wave (FLAPW) method. The results obtained with the two methods are in excellent agreement, demonstrating the ability of the LCGTO-FF method to address the properties of a light actinide metal in its low-symmetry a phase.