Low-temperature formation of cubic β-PbF2: precursor-based synthesis and first-principles phase stability study

Abstract

A precursor-based approach to the cubic β-phase of PbF₂ was developed and allowed the preparation of this high-temperature phase well below the temperature for transition from the orthorhombic α- to the cubic β-phase. The formation of β-PbF₂ from the molecular precursors Pb[Se(C₆H₂(CF₃)₃)]₂ and Pb(C₆H₂(CF₃)₃)₂ is facilitated by the presence of several short Pb⋯F contacts in these molecules. The cubic form of PbF₂ 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 β-phase is slightly lower than the one for the α-phase, by 0.5–1.7 kJ mol⁻¹ depending on the density functional used (zero-point vibrational energy correction included).