Treating the I− anion as a zero-electron system: the LiI− and CsI− alkali halides anions

The accuracy of a full core treatment of the I − anion based on a zero-electron pseudo-potential (ZEP) including core polarization pseudo-potential (CPP) is examined on reference compounds LiI − and CsI − considered as one-electron systems. The results are compared to ab initio CASPT 2 calculations involving 8 active electrons on iodine and 3 (respectively, 9) on lithium (respectively, cesium). An original scheme is proposed to build a pseudo-potential describing the short-range electron–I − interaction beyond the point charge approximation. The importance of the ZEP in one-electron calculations is estimated for the mentioned anions.