  We extend the Vanderbilt ultrasoft pseudopotential scheme by adding kinetic
energy density terms, in order to use meta-GGA exchange potentials, such as the
Becke-Johnson or Tran-Blaha potentials, in the planewave-pseudopotential
implementation of Density Functional Theory. Having implemented kinetic energy
augmentation and non-linear core correction terms in the CASTEP density
functional package, we evaluate the validity of our approach by comparing the
calculated electronic structure of isolated atoms and semiconductor crystals to
all-electron benchmark calculations. Based on our results, we provide
recommendations for the practical use of the Tran-Blaha exchange in
planewave-pseudopotential codes.
