Schematic atomic structure of relaxed 1CaTcO3/1BaTcO3 superlattice at theoretical DFT ground state with monoclinic space group symmetry Pc.
Schematic atomic structure of relaxed 1CaTcO3/1BaTcO3 superlattice at theoretical DFT ground state with monoclinic space group symmetry Pc.

We carry out systematic studies of the structural instabilities of the new perovskite family ATcO3 (A = Ca, Sr, Ba) by first-principles calculations. The orthorhombic ground state of CaTcO3 and SrTcO3 are found to be closely related to structural distortions due to the zone boundary phonon instabilities. We also identify a weak ferroelectric instability in CaTcO3, which is however suppressed at the ground state due to the large antiferrodistortive mode. We show that the ferroelectricity in CaTcO3 can be induced in the CaTcO3/BaTcO3 superlattices. Two types of interface mechanisms are involved, one is realized by the mismatch of the antipolar modes between two parent bulk materials and the other is the suppression of antiferrodistortive mode at interface. The Néel temperature of CaTcO3/BaTcO3 superlattices is found to be ∼∼816 K, indicating that CaTcO3 can be engineered into a new room temperature multiferroic material.

This paper was originally published in Computational Materials Science 96 (2015) 171–177

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