Two-electron tin centers with a negative correlation energy in lead sulfide

Abstract

The valence and coordination states of the impurity tin centers in the lead sulfide crystal lattice were determined by emission Mössbauer spectroscopy. Tin atoms that replace lead atoms are two electron donors with negative correlation energy. The correlation energy U = -0.072 ± 0.004 eV, as well as the posi tions of the first (E V + E 1 = 0.079 ± 0.002 eV) and second (E V + E 2 = 0.151 ± 0.004 eV) ionization energies, were determined (E V is the energy of the top of valence band).