http://www.physics.rutgers.edu/~dhv/uspp/uspp-cur/Work/008-O/008-O-gpbe--bm

Warning: this O psp has been tested in liquid water simulations by 
Patrick Sit and Nicola Marzari. Results for the diffusion coefficient
and pair correlation functions were at odd with those obtained with 
other ultrasoft or norm-conserving pseudopotentials, and recently
published results.