The CASTEP authors have some presentations and information that discusses using the sX-LDA functional for accurate band structure information for semiconductors.  In the current version of CASTEP, the density mixing scheme does not work, so they suggest using fixed occupancy, and using the Allbands/EDFT SCF solver.  These are easy enough to set up from Materials Studio, but they also suggest using divergence correction to accelerate k-point convergence.

After extensively searching for help on this matter in the CASTEP help, I have come up with nothing.  However, the output files indicate in the "Exchange Correlation Parameters" that Divergence Correction is "Off".  What keyword in the *.param input file allows one to turn divergence correction on?

I am specifically referring to:

ftp://ftp.nd.rl.ac.uk/scratch/KeithRefson/Accelrys/SX_LDAU.pdf

As well as Physical Rev. B 2010, 82, 058208 "Screened exchange density functional applied to solids" and Phys. Rev. B 2010, 81, 115311 "Intrinsic defects in ZnO calculated by screened exchange and hybrid density functionals".