Libxc (a library of exchange-correlation functionals for 
 density-functional theory)

Libxc is a library of exchange-correlation and kinetic energy
 functionals for density-functional theory. The original aim 
was to provide a portable, well tested and reliable set of 
these functionals to be used by all the codes of the European 
Theoretical Spectroscopy Facility (ETSF), but the library has
 since grown to be used in several other types of codes as well.