Ab InitioStudy of Divalent 3dTransition Metal Impurities in KMgF3and BaLiF3

Divalent 3 d transition metal impurities (V, Cr, Mn, Fe, Co, Ni, and Cu) in KMgF 3 and BaLiF 3 have been investigated by local-spin-density approximation (LSDA)-based ab initio calculations using an ultrasoft pseudopotential method and a planewave basis set. The results of numerical calculations show that the 3 d transition metal impurities exhibit mid-gap levels and that the electronic transition from impurity levels to the conduction band results from the absorption of vacuum ultraviolet (VUV) light with energy lower than band-gap width. Therefore, 3 d transition metal contaminations in KMgF 3 and BaLiF 3 should be avoided for VUV lithographic lens applications.