Ghost states

The fully separable form of pseudopotential would possess artificial ghost states [13], which is one of serious problems in the separable form, while multiple projectors proposed by Blöchl [6] is highly effective to avoid the existence of ghost states. To check it, a keyword, ghost.check, is provided. Although the keyword is useful to find the ghost states, however, it should be noted that a complete check to detect the ghost states is difficult.