Bader's analysis of the electron density in the Pbca enstatite - Pbcn protoenstatite phase transition

The Bader's topological analysis of the electron density obtained via ab initio quantum mechanical simulation at Hartree-Fock and DFT level has been performed for experimentally in situ heated structures of enstatite-protoenstatite MgSiO(3). The measurements have been performed in the temperature range 1200-1400 K. The work was aimed at characterizing both the evolution of the electron arrangement in the crystal and that of the crystal-structure at the enstatite-protoenstatite phase transition in terms of topology of the electron density, with particular care about the Mg-O and the O-O bonds. The observed breaking of some chemical bonds with increasing temperature and/or due to the phase transformation have been explained, for the first time, in the light of a topological mechanism based on the Catastrophe Theory applied to the framework of the Bader's theory.