Low-temperature formation of cubic beta-PbF(2): precursor-based synthesis and first-principles phase stability study

Abstract

A precursor-based approach to the cubic beta-phase of PbF(2) was developed and allowed the preparation of this high-temperature phase well below the temperature for transition from the orthorhombic alpha- to the cubic beta-phase. The formation of beta-PbF(2) from the molecular precursors Pb[Se(C(6)H(2)(CF(3))(3))](2) and Pb(C(6)H(2)(CF(3))(3))(2) is facilitated by the presence of several short Pb center dot center dot center dot F contacts in these molecules. The cubic form of PbF(2) was obtained as macroscopic crystals as well as nanoparticulate powder. Its formation at relatively low temperature suggested a theoretical re-investigation of the phase stabilities of the two polymorphs. The theoretical results from the Kohn-Sham density functional theory indicate that the energy content for the beta-phase is slightly lower than the one for the alpha-phase, by 0.5-1.7 kJ mol(-1) depending on the density functional used (zero-point vibrational energy correction included).