Estimation of inter-atomic force constants and phonon dispersion using correlation effects among thermal displacement of atoms in Ge

• Published in: Journal of non-crystalline solids Vol. 357; no. 2; pp. 559 - 562
• Main Authors: Sakuma, Takashi, Mohapatra, Saumya R., Isozaki, Nobuhiro, Uehara, Hiroyuki, Xianglian, Basar, Khairul, Takahashi, Haruyuki, Kamishima, Osamu, Igawa, Naoki
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier B.V 15.01.2011; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Constants; Correlation; Correlation effects; Crystal structure; Diffuse scattering; Diffusion; Dispersions; Displacement; Exact sciences and technology; Force constant; Germanium; Lattice dynamics; Neutron diffraction and scattering; Neutron scattering; Neutron scattering techniques (including small-angle scattering); Phonon; Phonons and vibrations in crystal lattices; Physics; Scattering; Single-crystal and powder diffraction; Structure of solids and liquids; crystallography; Force constant; Neutron scattering; Diffuse scattering; Ge; Phonon; Correlation effects; Temperature dependence; Rietveld method; Crystallographic direction; Correlation theory; Neutron diffraction; Interatomic forces; Dispersion relations; Phonons; Force constants; Neutron diffusion; Scattering theory; Debye temperature; Atomic displacements; Phonon dispersion; Interatomic distances; Phonon spectra; Crystal structure
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2010.06.054

Neutron diffraction measurements have been performed on powder Ge at 6, 150 and 300 K. Oscillatory diffuse scattering intensity is clearly observed at 150 and 300 K. The diffuse scattering theory including correlation effects among thermal displacements of atoms is applied to background function in the Rietveld analysis. The inter-atomic distance and temperature dependence of the values of correlation effects are discussed. The force constants among the first, second and third nearest neighboring atoms in Ge are obtained from the values of correlation effects and Debye–Waller temperature parameters. A phonon dispersion spectrum in Λ [111] direction for Ge crystal has also been calculated at 80 K using inter-atomic force constants and the crystal structure.