Application of Nuclear Inelastic Scattering Spectroscopy to the Frequency Scale Calibration of Ab Initio Calculated Phonon Density of States of Quasi-One-Dimensional Ternary Iron Chalcogenide RbFeSe2

Airat Kiiamov,Vladimir Tsurkan,Dmitrii Tayurskii,Lenar Tagirov,Zakir Seidov,Hans-Albrecht Krug Von Nidda,Ilya Sergueev,Dorina Croitori,Hans-Christian Wille,Olaf Leupold

doi:10.3390/app10207212

Abstract

This study aims to examine the applicability of nuclear inelastic scattering (NIS) and conventional Mössbauer spectroscopy for calibration of the frequency scale of ab initio calculated phonon density of states (PDOS) of iron ternary chalcogenides. NIS measurements are carried out on the quasi-one-dimensional ternary chalcogenide RbFeSe2 to obtain the partial PDOS of the iron atoms in the compound. We compare the experimental PDOS with our previous results on vibrational properties of RbFeSe2 obtained with density functional theory (DFT) ab initio calculations, conventional Mössbauer, and infra-red spectroscopies. The experimental PDOS measured by NIS is collated with the ab initio calculated one. The frequency correction factor for the ab initio results is determined as 1.077, in good agreement with value of 1.08 obtained previously from the temperature dependence of the Lamb–Mössbauer factor of the iron atoms in RbFeSe2. We conclude that nuclear inelastic scattering and temperature dependence of the Lamb–Mössbauer factor in conventional Mössbauer spectroscopy can be equally applied for evaluation of the frequency correction factor for ab initio calculated phonon density of iron of ternary chalcogenides.

Highlights

Specific heat is one of the most informative features of a solid
Our study revealed that the phenomenological description of the temperature dependence of the heat capacity of the chain iron chalcogenides is not constructive, because of the strongly non-Debye type of the phonon density of states (PDOS), Figure 2, and due to the inability of calibrating the absolute value of the lattice contribution to the heat capacity, without which it is impossible to separate quantitatively the magnetic contribution to the heat capacity from the lattice one
We presented the results of 57 Fe nuclear inelastic scattering measurements of the quasi-onedimensional antiferromagnet RbFeSe2

Summary

Introduction

Specific heat is one of the most informative features of a solid. The temperature dependence of the specific heat of solids enables the detection of any type of phase transition of different origin. Specific-heat investigations are quite useful in studies of complex magnetic. Sci. 2020, 10, 7212 systems, see [1] for instance. The correctness of an anticipated spin-Hamiltonian and corresponding approximations to describe a certain magnetic system can be checked by comparison of the experimental specific-heat data with the theoretical predictions derived from the model (see, for example, [2])

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