title: Debye-Waller coefficient of heavily deformed nanocrystalline iron.
abstract: Synchrotron radiation X-ray diffraction (XRD) patterns from an extensively ball-milled iron alloy powder were collected at 100, 200 and 300 K. The results were analysed together with those using extended X-ray absorption fine structure, measured on the same sample at liquid nitrogen temperature (77 K) and at room temperature (300 K), to assess the contribution of static disorder to the Debye-Waller coefficient (Biso). Both techniques give an increase of ∼20% with respect to bulk reference iron, a noticeably smaller difference than reported by most of the literature for similar systems. Besides good quality XRD patterns, proper consideration of the temperature diffuse scattering seems to be the key to accurate values of the Debye-Waller coefficient. Molecular dynamics simulations of nanocrystalline iron aggregates, mapped on the evidence provided by XRD in terms of domain size distribution, shed light on the origin of the observedBisoincrease. The main contribution to the static disorder is given by the grain boundary, while line and point defects have a much smaller effect.
authors.affiliation: Department of Civil, Environmental and Mechanical Engineering, University of Trento, Trento, Italy.
authors.forename: P
authors.identifier: https://orcid.org/0000-0003-1097-3917
authors.initials: P
authors.lastname: Scardi
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., Trieste, Italy.
authors.forename: L
authors.identifier: https://orcid.org/0000-0001-5779-1948
authors.initials: L
authors.lastname: Rebuffi
authors.affiliation: Synchrotron Light for Experimental Science and Applications in the Middle East - SESAME, Allan, Jordan.
authors.forename: M
authors.initials: M
authors.lastname: Abdellatief
authors.affiliation: Department of Civil, Environmental and Mechanical Engineering, University of Trento, Trento, Italy.
authors.forename: A
authors.identifier: https://orcid.org/0000-0002-1234-3858
authors.initials: A
authors.lastname: Flor
authors.affiliation: Department of Geological Sciences, Indiana University, Bloomington, Indiana, USA.
authors.forename: A
authors.identifier: https://orcid.org/0000-0003-2949-529X
authors.initials: A
authors.lastname: Leonardi
keywords: Debye–Waller coefficient; EXAFS; molecular dynamics; nanocrystalline materials; plastically deformed materials; synchrotron radiation X-ray diffraction; temperature diffuse scattering