Changes in the phonon density of states of Fe induced by external strain

Robert Meyer,Matthias W Klein,Volker Schünemann,Marek Smaga,Tilmann Beck,Sakshath Sadashivaiah,Tim Hochdörffer,Lena Scherthan,Juliusz A Wolny,Herbert M Urbassek

doi:10.1007/s00339-020-04169-y

Robert Meyer, Matthias W Klein + Show 8 more

Open Access

https://doi.org/10.1007/s00339-020-04169-y

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Journal: Applied physics	Publication Date: Dec 17, 2020
Citations: 5	License type: open-access

Affiliation: University of Kaiserslautern

Abstract

Nuclear inelastic scattering of synchrotron radiation is used to study the changes induced by external tensile strain on the phonon density of states (pDOS) of polycrystalline Fe samples. The data are interpreted with the help of dedicated atomistic simulations. The longitudinal phonon peak at around 37 meV and also the second transverse peak at 27 meV are decreased under strain. This is caused by the production of defects under strain. Also the thermodynamic properties of the pDOS demonstrate a weakening of the force constants and of the mean phonon energy under strain. Remaining differences between experiment and simulation are discussed.

Highlights

The phonon density of states constitutes a fundamental characteristics of a solid
We present experimental data of the phonon density of states (pDOS) of Fe obtained by nuclear inelastic scattering (NIS)
To analyze and interpret the changes of the pDOS under strain, we calculate data for the pDOS of Fe using molecular dynamics simulation.These data were obtained in a way as described in [8] for a polycrystalline Fe sample with a grain size of around 10 nm; the sample contains around N = 250,000 atoms

Summary

Introduction

The phonon density of states (pDOS) constitutes a fundamental characteristics of a solid. For Fe the method of nuclear inelastic scattering (NIS) of synchrotron radiation can be used to measure this quantity [1] This method allows to study the changes of the pDOS in situations relevant for applications, such as in fatigue test used in materials science [2]. Synchrotron based NIS is able to deliver the pDOS of 57 Fe containing samples and of single micrometer-sized objects, thin films and even monolayers. This motivates the present study which paves the way for future investigations of defects and grain boundaries in micro- and possibly nano-objects. The comparison will allow us to interpret the changes induced by strain and to discuss the origin of the remaining differences between experiment and simulation

Experimental method

Results and discussion

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Conclusions