Stable Polar Oxynitrides through Epitaxial Strain

We investigate energetically favorable structures of ABO\(_2\)N oxynitrides as functions of pressure and strain via swarm-intelligence-based structure prediction methods, DFT lattice dynamics and first-principles molecular dynamics. We predict several thermodynamically stable polar oxynitride perovs...

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Bibliographic Details
Published inarXiv.org
Main Authors Zhu, Li, Takenaka, Hiroyuki, Cohen, R E
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 10.06.2021
Subjects
Atomic layer epitaxy
Dynamic stability
Ferroelectric materials
Ferroelectricity
Oxynitrides
Perovskites
Pressure
Pulsed laser deposition
Pulsed lasers
Substrates
Synthesis
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Summary:We investigate energetically favorable structures of ABO\(_2\)N oxynitrides as functions of pressure and strain via swarm-intelligence-based structure prediction methods, DFT lattice dynamics and first-principles molecular dynamics. We predict several thermodynamically stable polar oxynitride perovskites under high pressures. In addition, we find that ferroelectric polar phases of perovskite-structured oxynitrides can be thermodynamically stable and synthesized at high pressure on appropriate substrates. The dynamical stability of the ferroelectric oxynitrides under epitaxial strain at ambient pressure also imply the possibility to synthesize them using pulsed laser deposition or other atomic layer deposition methods. Our results have broad implications for further exploration of other oxynitride materials as well. We performed first-principles molecular dynamics and find that the polar perovskite of YSiO\(_2\)N is metastable up to at least 600 K under compressive epitaxial strain before converting to the stable wollastonite-like structures. YSiO\(_2\)N is stabilized under pressure with extensional epitaxial strain. We predict that LaSi\(_2\)N, LaGeO\(_2\)N, BiSiO\(_2\)N, and BiGeO\(_2\)N are metastable as ferroelectric perovskites at zero pressure even without epitaxial strain.
ISSN:2331-8422