Tunable Negative Thermal Expansion in Layered Perovskites from Quasi-Two-Dimensional Vibrations

Liang Feng Huang, Xue Zeng Lu, James M. Rondinelli

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

We identify a quasi-two-dimensional (quasi-2D) phonon mode in the layered-perovskite Ca3Ti2O7, which exhibits an acoustic branch with quadratic dispersion. Using first-principles methods, we show this mode exhibits atomic displacements perpendicular to the layered [CaTiO3]2 blocks comprising the structure and a negative Grüneisen parameter. Owing to these quasi-2D structural and dynamical features, we find that the mode can be utilized to realize unusual membrane effects, including a tunable negative thermal expansion (NTE) and a rare pressure-independent thermal softening of the bulk modulus. Detailed microscopic analysis shows that the NTE relies on strong intralayer Ti - O covalent bonding and weaker interlayer interactions, which is in contrast to conventional NTE mechanisms for perovskites, such as rigid-unit modes, structural transitions, and electronic or magnetic ordering. The general application of the quasi-2D lattice dynamics opens exciting avenues for the control of lattice dynamical and thermodynamic responses of other complex layered compounds through rational chemical substitution, as we show in A3Zr2O7 (A=Ca, Sr), and by heterostructuring.

Original languageEnglish (US)
Article number115901
JournalPhysical review letters
Volume117
Issue number11
DOIs
StatePublished - Sep 7 2016

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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