Q. Core-electron excitation and ionization

 

A. The basis sets should be flexible enough to describe orbital reorganizations and electron correlations.  The polarization functions of inner-shell orbital, first derivatives of 1s functions, i.e. p-type functions, are necessary for describing the polarizations and the angular correlations of the 1s electrons. See, for example, J. Chem. Phys. 122, 014304 (2005).