Monte Carlo Modeling of Diffuse Scattering from Single Crystals: The Program 
                ZMC

Goossens, Darren; Heerdegen, Aidan; Chan, Eric J.; Welberry, T. R.

doi:10.1007/s11661-010-0199-1

Cited by 34 publications

(34 citation statements)

References 24 publications

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“…MC models used to calculate diffuse scattering consist of an array of 48 Â 48 Â 48 unit cells, each of which initially contains atomic coordinates taken from the Bragg structure as mentioned in the previous section. Correlated displacements are generated using the program ZMC (Goossens et al, 2010).…”

Section: Simulation Details and Calculation Of Diffuse Intensitiesmentioning

confidence: 99%

“…The data fitting procedure uses three reciprocal space basal planes and large portions of the Bragg scattering profile is removed, because it is not calculated by the diffuse scattering calculation. The individual MC simulations are implemented using the program ZMC (Goossens et al, 2010). Previous work using this approach has presented correlations amongst positional displacements using polar plots (Goossens et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…The individual MC simulations are implemented using the program ZMC (Goossens et al, 2010). Previous work using this approach has presented correlations amongst positional displacements using polar plots (Goossens et al, 2010). Here, a method for representing correlations amongst orientations of molecules is presented, the intention being to explore the presence of correlated molecular rotations, a phenomenon likely to be required if form (II) is to transform into form (I).…”

Section: Introductionmentioning

confidence: 99%

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Study of the single-crystal X-ray diffuse scattering in paracetamol polymorphs

Chan¹,

Goossens²

2012

Acta Crystallogr Sect B

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Single-crystal diffuse X-ray scattering from paracetamol polymorphs is successfully calculated with Monte Carlo (MC) models that are used to simulate the crystals. In order to obtain the correct model appropriate force constants are required that describe the interatomic potentials used in the MC algorithm. Coefficients for an empirical 'Buckingham'-type formula are used to determine these force constants. These coefficients are subsequently refined using the least-squares method and are found to converge on similar values for both polymorphic forms. An investigation of the correlation space generated from each model provides what would be expected given that strong displacive correlations exist between the molecules comprising the densely hydrogen-bonded layers. More disordered motions between these layers are present in the model for form (II) as opposed to form (I). An investigation into the peculiarities of librational disorder was also conducted, however, correlation values turn out to be so small that any structural information concerning librational correlation is inconclusive. The purpose of this experiment was to identify if the diffuse scattering features could provide further insight into understanding the physical reasoning behind the metastability of form (II). The form (II) → (I) phase transition is also not currently well understood and usually phase transitional information can be obtained from pronounced diffuse scattering features. Since the diffuse scattering is modelled adequately using harmonic potentials it is our conjecture that the 'diffuse' is essentially thermal in origin and does not afford any extra information about the form (II) → (I) phase transition.

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Section: Simulation Details and Calculation Of Diffuse Intensitiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Study of the single-crystal X-ray diffuse scattering in paracetamol polymorphs

Chan¹,

Goossens²

2012

Acta Crystallogr Sect B

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“…In recent years, much work has been done in making the analysis of single crystal diffuse scattering (SCDS) more routine [1][2][3][4][5][6]. While the technique can provide information about many subtle and important structural effects [7], there is no straightforward approach to analysing the data.…”

Section: Introductionmentioning

confidence: 99%

A Process for Modelling Diffuse Scattering from Disordered Molecular Crystals, Illustrated by Application to Monoclinic 9-Chloro-10-methylanthracene

Goossens

2015

Advances in Condensed Matter Physics

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Diffuse scattering from a crystal contains valuable information about the two-body correlations (related to the nanoscale order) in the material. Despite years of development, the detailed analysis of single crystal diffuse scattering (SCDS) has yet to become part of the everyday toolbox of the structural scientist. Recent decades have seen the pair distribution function approach to diffuse scattering (in fact, total scattering) from powders become a relatively routine tool. However, analysing the detailed, complex, and often highly anisotropic three-dimensional distribution of SCDS remains valuable yet rare because there is no routine method for undertaking the analysis. At present, analysis requires significant investment of time to develop specialist expertise, which means that the analysis of diffuse scattering, which has much to offer, is not incorporated thorough studies of many compounds even though it has the potential to be a very useful adjunct to existing techniques. This article endeavours to outline in some detail how the diffuse scattering from a molecular crystal can be modelled relatively quickly and largely using existing software tools. It is hoped this will provide a template for other studies. To enable this, the entire simulation is included as deposited material.

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“…If it is displacements that are of interest, the simplest choice is to connect atoms with Hooke's law springs The program ZMC [63] is designed to induce correlations amongst atomic and/or molecular displacements by causing the atoms to interact with surrounding atoms via Hooke's law springs of the form:…”

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Monte Carlo Modelling of Single-Crystal Diffuse Scattering from Intermetallics

Goossens

2016

Metals

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Single-crystal diffuse scattering (SCDS) reveals detailed structural insights into materials. In particular, it is sensitive to two-body correlations, whereas traditional Bragg peak-based methods are sensitive to single-body correlations. This means that diffuse scattering is sensitive to ordering that persists for just a few unit cells: nanoscale order, sometimes referred to as "local structure", which is often crucial for understanding a material and its function. Metals and alloys were early candidates for SCDS studies because of the availability of large single crystals. While great progress has been made in areas like ab initio modelling and molecular dynamics, a place remains for Monte Carlo modelling of model crystals because of its ability to model very large systems; important when correlations are relatively long (though still finite) in range. This paper briefly outlines, and gives examples of, some Monte Carlo methods appropriate for the modelling of SCDS from metallic compounds, and considers data collection as well as analysis. Even if the interest in the material is driven primarily by magnetism or transport behaviour, an understanding of the local structure can underpin such studies and give an indication of nanoscale inhomogeneity.

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Monte Carlo Modeling of Diffuse Scattering from Single Crystals: The Program ZMC

Cited by 34 publications

References 24 publications

Study of the single-crystal X-ray diffuse scattering in paracetamol polymorphs

Study of the single-crystal X-ray diffuse scattering in paracetamol polymorphs

A Process for Modelling Diffuse Scattering from Disordered Molecular Crystals, Illustrated by Application to Monoclinic 9-Chloro-10-methylanthracene

Monte Carlo Modelling of Single-Crystal Diffuse Scattering from Intermetallics

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