Some simple hybrids & XDM parameters
Some small changes related to hybrids and XDM:
- Implemented two new hybrids: B86BPBEx and Becke-halfandhalf-LYP. This gives access to the corresponding 20% and 25%-hybrids using exx_fraction.
- Print timing information from the XDM routines.
- Added default XDM parameters that differentiate between PAW/NC and also for old and new hybrid functionals.