New Insights into Complex Materials Using Reverse Monte Carlo Modeling

Playford, Helen Y.; Owen, Lewis; Levin, Igor; Tucker, Matthew G.

doi:10.1146/annurev-matsci-071312-121712

Cited by 60 publications

(54 citation statements)

References 72 publications

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“…The study of amorphous materials, which by definition lack the long-range order that leads to Bragg peaks, motivated the development of the total scattering technique, in which the Bragg and diffuse scattering from a sample are measured and analysed simultaneously. The technique has, more recently, been applied with great success to study many crystalline and disorderedcrystalline systems [10] providing insight into the local information through analysis of deviations from the average structure. The basic scattering function for neutrons [11] is given as:…”

Section: Total Scatteringmentioning

confidence: 99%

A new approach to the analysis of short-range order in alloys using total scattering

et al. 2016

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a b s t r a c tIn spite of its influence on a number of physical properties, short-range order in crystalline alloys has received little recent attention, largely due to the complexity of the experimental methods involved. In this work, a novel approach that could be used for the analysis of ordering transitions and short-range order in crystalline alloys using total scattering and reverse Monte Carlo (RMC) refinements is presented. Calculated pair distribution functions representative of different types of short-range order are used to illustrate the level of information contained within these experimentally accessible functions and the insight into ordering which may be obtained using this new method. Key considerations in the acquisition of data of sufficient quality for successful analysis are also discussed. It is shown that the atomistic models obtained from RMC refinements may be analysed to identify directly the Clapp configurations that are present. It is further shown how these configurations can be enhanced compared with a random structure, and how their degradation pathways and the distribution of Warren-Cowley parameters, can then be used to obtain a detailed, quantitative structural description of the short-range order occurring in crystalline alloys.

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Section: Total Scatteringmentioning

confidence: 99%

A new approach to the analysis of short-range order in alloys using total scattering

et al. 2016

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“…Total scattering and pair distribution function (PDF) analysis methods have been evolving rapidly in recent years (Farrow et al, 2007;Billinge & Levin, 2007;Playford et al, 2014;Egami & Billinge, 2012;Keen & Goodwin, 2015;Mancini & Malavasi, 2015) as the advent of faster computers has allowed for increasingly complex modeling programs such as RMCProfile (Tucker et al, 2007), DEBUSSY (Cervellino et al, 2015) and FullRMC (Aoun, 2016), to address longer length-scale correlations. At the same time, the complexity of many modern material studies often involves characterizing the structural correlations and nanoscale ordering at length scales on the order of tens to hundreds of å ngströ ms (Aksel et al, 2013;Coduri et al, 2013;Hill & Allieta, 2013;Usher et al, 2015;Allieta et al, 2015;Checchia et al, 2015;Liu et al, 2016Liu et al, , 2017Jiang et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Precise implications for real-space pair distribution function modeling of effects intrinsic to modern time-of-flight neutron diffractometers

Olds

Saunders

Peters

et al. 2018

Acta Crystallogr A Found Adv

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Total scattering and pair distribution function (PDF) methods allow for detailed study of local atomic order and disorder, including materials for which Rietveld refinements are not traditionally possible (amorphous materials, liquids, glasses and nanoparticles). With the advent of modern neutron time-of-flight (TOF) instrumentation, total scattering studies are capable of producing PDFs with ranges upwards of 100-200 Å, covering the correlation length scales of interest for many materials under study. Despite this, the refinement and subsequent analysis of data are often limited by confounding factors that are not rigorously accounted for in conventional analysis programs. While many of these artifacts are known and recognized by experts in the field, their effects and any associated mitigation strategies largely exist as passed-down `tribal' knowledge in the community, and have not been concisely demonstrated and compared in a unified presentation. This article aims to explicitly demonstrate, through reviews of previous literature, simulated analysis and real-world case studies, the effects of resolution, binning, bounds, peak shape, peak asymmetry, inconsistent conversion of TOF to d spacing and merging of multiple banks in neutron TOF data as they directly relate to real-space PDF analysis. Suggestions for best practice in analysis of data from modern neutron TOF total scattering instruments when using conventional analysis programs are made, as well as recommendations for improved analysis methods and future instrument design.

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“…The reverse Monte Carlo (RMC) algorithm is one of the most popular methods for producing atomistic models from experimental data as it can produce large (thousands of atoms) supercells consistent with a given set of data (typically diffraction data) through iterated small random atomistic moves 9,10 . The randomness inherent in the RMC algorithm causes the refined models to contain the maximum amount of disorder that is consistent with the experimental data.…”

Section: Introductionmentioning

confidence: 99%

Structural simplicity as a restraint on the structure of amorphous silicon

et al. 2017

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Understanding the structural origins of the properties of amorphous materials remains one of the most important challenges in structural science. In this study we demonstrate that local 'structural simplicity', embodied by the degree to which atomic environments within a material are similar to each other, is powerful concept for rationalising the structure of canonical amorphous material amorphous silicon (a-Si). We show, by restraining a reverse Monte Carlo refinement against pair distribution function (PDF) data to be simpler, that the simplest model consistent with the PDF is a continuous random network (CRN). A further effect of producing a simple model of a-Si is the generation of a (pseudo)gap in the electronic density of states, suggesting that structural homogeneity drives electronic homogeneity. That this method produces models of a-Si that approach the state-of-the-art without the need for chemically specific restraints (beyond the assumption of homogeneity) suggests that simplicity-based refinement approaches may allow experiment-driven structural modelling techniques to be developed for the wide variety of amorphous semiconductors with strong local order. arXiv:1609.00668v3 [cond-mat.mtrl-sci]

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New Insights into Complex Materials Using Reverse Monte Carlo Modeling

Cited by 60 publications

References 72 publications

A new approach to the analysis of short-range order in alloys using total scattering

A new approach to the analysis of short-range order in alloys using total scattering

Precise implications for real-space pair distribution function modeling of effects intrinsic to modern time-of-flight neutron diffractometers

Structural simplicity as a restraint on the structure of amorphous silicon

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