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Title: Analysis of the crystal lattice instability for cage–cluster systems using the superatom model

Abstract

We have investigated the lattice dynamics for a number of rare-earth hexaborides based on the superatom model within which the boron octahedron is substituted by one superatom with a mass equal to the mass of six boron atoms. Phenomenological models have been constructed for the acoustic and lowenergy optical phonon modes in RB{sub 6} (R = La, Gd, Tb, Dy) compounds. Using DyB{sub 6} as an example, we have studied the anomalous softening of longitudinal acoustic phonons in several crystallographic directions, an effect that is also typical of GdB{sub 6} and TbB{sub 6}. The softening of the acoustic branches is shown to be achieved through the introduction of negative interatomic force constants between rare-earth ions. We discuss the structural instability of hexaborides based on 4f elements, the role of valence instability in the lattice dynamics, and the influence of the number of f electrons on the degree of softening of phonon modes.

Authors:
;  [1];  [2]
  1. I. Kant Baltic Federal University, “Functional Nanomaterials” Scientific–Educational Center (Russian Federation)
  2. “Kurchatov Institute” National Research Center (Russian Federation)
Publication Date:
OSTI Identifier:
22617185
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Experimental and Theoretical Physics; Journal Volume: 123; Journal Issue: 3; Other Information: Copyright (c) 2016 Pleiades Publishing, Inc.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ACOUSTICS; ATOMS; CRYSTAL LATTICES; CRYSTALLOGRAPHY; CRYSTALS; DYSPROSIUM BORIDES; GADOLINIUM BORIDES; INSTABILITY; INTERATOMIC FORCES; MASS; PHONONS; RARE EARTH COMPOUNDS; VALENCE

Citation Formats

Serebrennikov, D. A., E-mail: dserebrennikov@innopark.kantiana.ru, E-mail: dimafania@mail.ru, Clementyev, E. S., and Alekseev, P. A. Analysis of the crystal lattice instability for cage–cluster systems using the superatom model. United States: N. p., 2016. Web. doi:10.1134/S1063776116070220.
Serebrennikov, D. A., E-mail: dserebrennikov@innopark.kantiana.ru, E-mail: dimafania@mail.ru, Clementyev, E. S., & Alekseev, P. A. Analysis of the crystal lattice instability for cage–cluster systems using the superatom model. United States. doi:10.1134/S1063776116070220.
Serebrennikov, D. A., E-mail: dserebrennikov@innopark.kantiana.ru, E-mail: dimafania@mail.ru, Clementyev, E. S., and Alekseev, P. A. Thu . "Analysis of the crystal lattice instability for cage–cluster systems using the superatom model". United States. doi:10.1134/S1063776116070220.
@article{osti_22617185,
title = {Analysis of the crystal lattice instability for cage–cluster systems using the superatom model},
author = {Serebrennikov, D. A., E-mail: dserebrennikov@innopark.kantiana.ru, E-mail: dimafania@mail.ru and Clementyev, E. S. and Alekseev, P. A.},
abstractNote = {We have investigated the lattice dynamics for a number of rare-earth hexaborides based on the superatom model within which the boron octahedron is substituted by one superatom with a mass equal to the mass of six boron atoms. Phenomenological models have been constructed for the acoustic and lowenergy optical phonon modes in RB{sub 6} (R = La, Gd, Tb, Dy) compounds. Using DyB{sub 6} as an example, we have studied the anomalous softening of longitudinal acoustic phonons in several crystallographic directions, an effect that is also typical of GdB{sub 6} and TbB{sub 6}. The softening of the acoustic branches is shown to be achieved through the introduction of negative interatomic force constants between rare-earth ions. We discuss the structural instability of hexaborides based on 4f elements, the role of valence instability in the lattice dynamics, and the influence of the number of f electrons on the degree of softening of phonon modes.},
doi = {10.1134/S1063776116070220},
journal = {Journal of Experimental and Theoretical Physics},
number = 3,
volume = 123,
place = {United States},
year = {Thu Sep 15 00:00:00 EDT 2016},
month = {Thu Sep 15 00:00:00 EDT 2016}
}