Investigation of structural, vibrational and ferroic properties of AgNbO3 at room temperature using neutron diffraction, Raman scattering and density-functional theory. (6th June 2015)

• Record Type: Journal Article
• Authors: Niranjan, Manish K; Ganga Prasad, K; Asthana, Saket; Rayaprol, S; Siruguri, V
• Is Part Of: Journal of physics. Volume 48:Number 21(2015)
• Page Start: 2795
• Page End: 2810
• Publication Date: 2015-06-06
• Subjects: Physics -- Periodicals; 530
• DOI: 10.1088/0022-3727/48/21/215303
• Languages: English
• ISSNs: 0022-3727

Abstract

<abstract> <title>Abstract</title> <p>We perform a comprehensive study of the structural, lattice dynamical and ferroic properties of the room temperature phase of AgNbO₃ using a combination of neutron diffraction, Raman spectroscopy and first-principles density functional theory. The Rietveld analysis of neutron diffraction data indicates that AgNbO₃ at room temperature crystallizes in an orthorombic structure with noncentrosymmetric <italic>Pmc</italic>2₁ space group symmetry. The zone-center phonon mode frequencies of <italic>Pmc</italic>2₁ and <italic>Pbcm</italic> phases of AgNbO₃ are computed and are found to be in good agreement with experimentally obtained Raman mode frequencies. Computed frequencies for both space groups are found to be very close. However, computed modes with frequencies 488 and 846 cm⁻¹ are found to be Raman-active for the <italic>Pmc</italic>2₁ phase while Raman inactive for <italic>Pbcm</italic> phase. The computed potential energy surfaces and Born effective charges of the ions suggest that the primary contribution to ferroic properties of AgNbO₃ come from Nb and O ions only. Furthermore the calculated potential energy profiles suggest competing ferroic and antiferrodistortive instabilities in AgNbO₃ are primarily due to the off-centering of Nb ions and rotations of NbO₆ octahedra, respectively.</p> </abstract>