Hardness conserving semilocal pseudopotentials

A new type of pseudopotentials for local orbital methods is presented. Hardness conserving semilocal pseudopotentials have been generated for all elements from H to Am. The construction is based on a minimization of errors with the norm conservation conditions for 2-3 relevant ionic configurations of the atom. Besides the transferability between atomic states, the portability among density functionals is also of interest. This paper explores if the norm-conservation errors can be kept reasonably small when minimized for two functionals, e.g., the generalized gradient approximation (GGA) and local density approximation, simultaneously. It is found that the errors can be kept at roughly the same low level as for a single functional. Since these pseudopotentials are mainly designed for use with local orbital methods, semicore functions may be treated as valence functions, helping to increase the accuracy and portability. Therefore the name density functional semicore pseudopotential or DSPP is suggested. To further improve portability and, importantly, also aid numerical stability with GGA's, a core density (nonlinear core correction) is used. As with other pseudopotentials, scalar relativistic corrections to atomic scattering properties can easily be incorporated into this PP. Finally performance DSPP's versus all electron DSPP's with the same method, will be shown for an extensive set of test calculations. It is found that the DSPP is a very well behaved pseudo-potential.