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Ab initio study of ferroelectricity in BaTiO3 nanowires G. Pilania, S. P. Alpay, and R. Ramprasad*

Summary: Ab initio study of ferroelectricity in BaTiO3 nanowires
G. Pilania, S. P. Alpay, and R. Ramprasad*
Chemical, Materials, and Biomolecular Engineering, Institute of Materials Science, University of Connecticut,
Storrs, Connecticut 06269, USA
Received 15 January 2009; revised manuscript received 19 May 2009; published 24 July 2009
We present a density-functional theory study of finite-size effects in stoichiometric and nonstoichiometric
BaTiO3 nanowires of varying cross-sectional sizes and sidewall terminations. The tendencies for axial, trans-
verse, and toroidal ferroelectric polarization instabilities in these nanowires have been characterized and pos-
sible driving forces underlying these behaviors have been identified. The critical size for ferroelectricity via
polarization along the nanowire axis is determined to be 12 , regardless of the stoichiometry or nanowire
sidewall terminations. The sidewall terminations alter the manner in which axial polarization manifests; for
instance, in nonstoichiometric BaO-terminated nanowires, a "core-shell-type" polarization results beyond the
critical size, while in all other cases, roughly uniform polarization along the same direction was observed
across the entire cross section. A tendency for transverse polarization i.e., normal to the nanowire axis occurs
in nanowires with a cross-sectional size of 16 displaying TiO2-terminated sidewall facets. This tendency is
accompanied by a toroidal or vortex polarization state, with the toroidal moment along the nanowire axis, to
mitigate the depolarizing fields due to transverse polarization.
DOI: 10.1103/PhysRevB.80.014113 PACS number s : 77.80. e, 77.22.Ej, 77.84.Dy
Owing to their potentially high dielectric constant and


Source: Alpay, S. Pamir - Department of Materials Science and Engineering, University of Connecticut


Collections: Materials Science