Lattice dynamics of orthorhombic NdGaO₃

Alyssa Mock, Linköping University, University of Nebraska
Rafal Korlacki, University of Nebraska-Lincoln
Sean Knight, University of Nebraska-Lincoln
Megan Stokey, University of Nebraska-Lincoln
A. Fritz, University of Nebraska, Lincoln
V. Darakchieva, Linköping University
Mathias Schubert, Linköping University, University of Nebraska - Lincoln, Leibniz Institute for Polymer Research

Document Type Article

Used by permission.

Abstract

A complete set of infrared-active and Raman-active lattice modes is obtained from density functional theory calculations for single-crystalline centrosymmetric orthorhombic neodymium gallate. The results for infraredactive modes are compared with an analysis of the anisotropic long-wavelength properties using generalized spectroscopic ellipsometry. The frequency-dependent dielectric function tensor and dielectric loss function tensor of orthorhombic neodymium gallium oxide are reported in the spectral range of 80–1200 cm⁻¹. A combined eigendielectric displacement vector summation and dielectric displacement loss vector summation approach augmented by considerations of lattice anharmonicity is utilized to describe the experimentally determined tensor elements. All infrared-active transverse and longitudinal optical mode pairs obtained from density functional theory calculations are identified by our generalized spectroscopic ellipsometry investigation. The results for Raman-active modes are compared to previously published experimental observations. Static and high-frequency dielectric constants from theory as well as experiment are presented and discussed in comparison with values reported previously in the literature.