We provide a straightforward and efficient procedure to combine LDA+U total energy functional with the full potential linearized augmented plane wave method. A detailed derivation of the LDA+U Kohn-Sham type equations is presented for the augmented plane wave basis set, and a simple "second-variation" based procedure for self-consistent LDA+U calculations is given. The method is applied to calculate electronic structure and magnetic properties of NiO and Gd. The magnetic moments and band eigenvalues obtained are in very good quantitative agreement with previous full potential LMTO calculations. We point out that LDA+U reduces the total d charge on Ni by 0.1 in NiO.

Unlike La2-vSr x Cu04, La2-.vBa x Cu04, JC~ x C r = 0.12, undergoes a structural change to a lowtemperature tetragonal (LTT) phase below 60 K, and this transformation is known to suppress T c drastically. We present self-consistent local-density-functional calculations for this system that indicate the Cu06 octahedrons are unstable to an Appoint tilt in any direction, thereby leading to strongly anharmonic Appoint vibrations. The LTT phase is most favored energetically, consistent with experiment. The effect of the LTT distortion on the electronic structure accounts for the suppression of T c in the LTT phase, and for the enhanced isotope effect at x =x CT . 8 JULY 1991 rAXYM E TAZURTA S Z T H _£> 1 • m 1 ^ 1 _>«. J "in J