  We devise a mixing algorithm for full-potential (FP) all-electron
calculations in the linearized augmented planewave (LAPW) method. Pulay's
direct inversion in the iterative subspace is complemented with the Kerker
preconditioner and further improvements to achieve smooth convergence, avoiding
charge sloshing and noise in the exchange-correlation potential. As the Kerker
preconditioner was originally designed for the planewave basis, we have adapted
it to the FP-LAPW method and implemented in the exciting code. Applications to
the $2\times 2$ Au(111) surface with a vacancy and to the Pd(111) surface
demonstrate that this approach and our implementation work reliably with both
density and potential mixing.
