Several experiments conducted over decades have revealed that the
perovskite-structured BaCeO3 goes through a series of temperature-induced
structural phase transitions. However, it has been frequently observed that the
number of phases and the sequence in which they appear as a function of
temperature differ between experiments. Insofar as neutron diffraction and
Raman spectroscopy experiments are concern, four structures are well
characterized with three transitions: Pnma to Imma [563 K] to R-3c [673 K] to
Pm-3m [1173 K]. In contrast, thermoanalytical methods showed multiple
singularities corresponding to at-least three more structural transitions at
around 830 K, 900 K, and 1030 K. In account of these conflicting experimental
findings, we computed free energy phase diagram for BaCeO3 employing crystal
structure data mining in conjunction with first principles electronic structure
and phonon lattice dynamics. A total of 34 polymorphs have been predicted, the
most stable of which follows the Glazer classification of the perovskite tilt
system. It has been predicted that the Cmcm and P4/mbm phases surpass Pnma at
666 K and 1210 K, respectively. At any temperature, two alternate tetragonal
phases (P42/nmc and I4/mcm) are also found to be 20 to 30 meV less favored than
the Pnma. While the calculated stability order of the predicted polymorphs is
in acceptable agreement with the results of neutron diffraction, the
transitions observed in thermoanalytical studies could be ascribed to the
development of four novel phases (Cmcm, P4/mbm, P42/nmc, and I4/mcm) at
intermediate temperatures. However, we analyze that the R-3c phase
predominantly stabilized over a broad temperature field, masking all subsequent
phases up until the cubic Pm-3m. Consequently, the novel phases predicted to
occur in thermoanalytical studies are only fleetingly metastable.Comment: 20 pages, 5 figures, 1 tabl