VASP is supplied with a set of standard pseudopotentials (PP), and we strongly urge all VASP users to rely on this set of PP or the PAW potentials (see Sec. 10.2). It was exceedingly difficult and time-consuming to generate these PP's. The main reason for making a set of potentials available is to eliminate the need for tedious tests. By relying on a world wide user base, we can (almost) guarantee that the potentials will work well for most applications. PP generation was, and still is, a tricky, cumbersome, error-prone and time-consuming task, and only few groups can afford to generate a new PP for every problem at hand.
The potentials supplied with VASP are among the best pseudopotentials presently available, but the pseudopotential method has been superseded by better electronic structure methods, such as the PAW method. Hence, the development of the ultra soft pseudopotentials distributed with VASP has come to an end, and we strongly recommend to use the PAW datasets now supplied in the VASP-PAW package (see Sec. 10.2).