Algorithm for systematic peak extraction from atomic pair distribution functions

2015 ◽  
Vol 71 (4) ◽  
pp. 392-409 ◽  
Author(s):  
L. Granlund ◽  
S. J. L. Billinge ◽  
P. M. Duxbury
Keyword(s):  
Structural Model ◽  
Information Criterion ◽  
Distribution Functions ◽  
Theory And Practice ◽  
Chi Square ◽  
Information Theoretic ◽  
Atomic Pair ◽  
Structure Solution ◽  
The Impact ◽  
Pair Distribution Functions

The study presents an algorithm, ParSCAPE, for model-independent extraction of peak positions and intensities from atomic pair distribution functions (PDFs). It provides a statistically motivated method for determining parsimony of extracted peak models using the information-theoretic Akaike information criterion (AIC) applied to plausible models generated within an iterative framework of clustering and chi-square fitting. All parameters the algorithm uses are in principle known or estimable from experiment, though careful judgment must be applied when estimating the PDF baseline of nanostructured materials. ParSCAPE has been implemented in the Python programSrMise. Algorithm performance is examined on synchrotron X-ray PDFs of 16 bulk crystals and two nanoparticles using AIC-based multimodeling techniques, and particularly the impact of experimental uncertainties on extracted models. It is quite resistant to misidentification of spurious peaks coming from noise and termination effects, even in the absence of a constraining structural model. Structure solution from automatically extracted peaks using the Liga algorithm is demonstrated for 14 crystals and for C60. Special attention is given to the information content of the PDF, theory and practice of the AIC, as well as the algorithm's limitations.

scholarly journals Crystal structure solution from experimentally determined atomic pair distribution functions

2010 ◽  
Vol 43 (3) ◽  
pp. 623-629 ◽  
Author(s):  
P. Juhás ◽  
L. Granlund ◽  
S. R. Gujarathi ◽  
P. M. Duxbury ◽  
S. J. L. Billinge
Keyword(s):  
Crystal Structure ◽  
Distribution Functions ◽  
Unit Cell ◽  
Second Step ◽  
X Ray ◽  
Atomic Pair ◽  
Structure Solution ◽  
Pair Distribution Functions ◽  
Atomic Radii ◽  
Periodic Crystal

An extension of the Liga algorithm for structure solution from atomic pair distribution functions (PDFs), to handle periodic crystal structures with multiple elements in the unit cell, is described. The procedure is performed in three separate steps. First, pair distances are extracted from the experimental PDF. In the second step the Liga algorithm is used to find unit-cell sites consistent with these pair distances. Finally, the atom species are assigned over the cell sites by minimizing the overlap of their empirical atomic radii. The procedure has been demonstrated on synchrotron X-ray PDF data from 16 test samples. The structure solution was successful for 14 samples, including cases with enlarged supercells. The algorithm success rate and the reasons for the failed cases are discussed, together with enhancements that should improve its convergence and usability.

scholarly journals The Impact of Brand Equity on Employee’s Opportunistic Behavior: A Case Study on Enterprises in Vietnam

2021 ◽  
Vol 14 (4) ◽  
pp. 164
Author(s):  
Quang Bach Tran ◽  
Quoc Hoi Le ◽  
Hoai Nam Nguyen ◽  
Dieu Linh Tran ◽  
Thi Thuy Quynh Nguyen ◽  
...  
Keyword(s):  
Employee Engagement ◽  
Brand Equity ◽  
Structural Equation ◽  
Structural Model ◽  
Negative Impact ◽  
Theory And Practice ◽  
Emotional Engagement ◽  
Opportunistic Behavior ◽  
Corporate Brand ◽  
The Impact

Brand is considered a valuable asset that a business wants to create and maintain growth throughout its business cycle. This paper examines the impact of corporate brand equity on employees’ opportunistic behavior. The paper uses quantitative research methods, through linear SEM (Structural Equation Modelling) analysis of structural model with a scale of 609 samples of employees of enterprises in Vietnam. The research results show that corporate brand equity has a negative impact on employees’ opportunistic behavior. In the relationship between these two factors, trust and emotional engagement act as intermediate factors. Additionally, the research demonstrates that trust has a positive effect on all three components of employee engagement, including emotional engagement, computational engagement, and standards-based engagement. On that basis, the research suggests a number of recommendations to minimize the opportunistic behavior of employees in the enterprise. The findings of this study have shown the importance and impact of brand equity on employee opportunistic behavior. These are meaningful contributions in both theory and practice to help businesses gain deeper insight into brand equity and the need to pay attention to building and developing durable brand equity for businesses. At the same time, it is an important basis for the next research projects.

Atomic pair distribution functions analysis of disordered low-Z materials

2013 ◽  
Vol 15 (22) ◽  
pp. 8544 ◽  
Author(s):  
V. Petkov ◽  
Y. Ren ◽  
S. Kabekkodu ◽  
D. Murphy
Keyword(s):  
Distribution Functions ◽  
Atomic Pair ◽  
Pair Distribution Functions

Selection of a Barley Yield Model Using Information–Theoretic Criteria

Weed Science ◽  
2008 ◽  
Vol 56 (4) ◽  
pp. 628-636 ◽  
Author(s):  
Marie Jasieniuk ◽  
Mark L. Taper ◽  
Nicole C. Wagner ◽  
Robert N. Stougaard ◽  
Monica Brelsford ◽  
...  
Keyword(s):  
Functional Form ◽  
Information Criterion ◽  
Small Sample ◽  
Theoretic Approach ◽  
Wild Oat ◽  
Information Theoretic ◽  
Information Theoretic Criteria ◽  
The Impact ◽  
Selection Of ◽  
Bioeconomic Models

Empirical models of crop–weed competition are integral components of bioeconomic models, which depend on predictions of the impact of weeds on crop yields to make cost-effective weed management recommendations. Selection of the best empirical model for a specific crop–weed system is not straightforward, however. We used information–theoretic criteria to identify the model that best describes barley yield based on data from barley–wild oat competition experiments conducted at three locations in Montana over 2 yr. Each experiment consisted of a complete addition series arranged as a randomized complete block design with three replications. Barley was planted at 0, 0.5, 1, and 2 times the locally recommended seeding rate. Wild oat was planted at target infestation densities of 0, 10, 40, 160, and 400 plants m−2. Twenty-five candidate yield models were used to describe the data from each location and year using maximum likelihood estimation. Based on Akaike's Information Criterion (AIC), a second-order small-sample version ofAIC(AICc), and the Bayesian Information Criterion (BIC), most data sets supported yield models with crop density (Dc), weed density (Dw), and the relative time of emergence of the two species (T) as variables, indicating that all variables affected barley yield in most locations.AIC,AICc, andBICselected identical best models for all but one data set. In contrast, the Information Complexity criterion,ICOMP, generally selected simpler best models with fewer parameters. For data pooled over years and locations,AIC,AICc, andBICstrongly supported a single best model with variablesDc,Dw,T, and a functional form specifying both intraspecific and interspecific competition.ICOMPselected a simpler model withDcandDwonly, and a functional form specifying interspecific, but no intraspecific, competition. The information–theoretic approach offers a rigorous, objective method for choosing crop yield and yield loss equations for bioeconomic models.

Modelling pair distribution functions (PDFs) of organic compounds: describing both intra- and intermolecular correlation functions in calculated PDFs

2015 ◽  
Vol 48 (1) ◽  
pp. 171-178 ◽  
Author(s):  
Dragica Prill ◽  
Pavol Juhás ◽  
Martin U. Schmidt ◽  
Simon J. L. Billinge
Keyword(s):  
Structural Models ◽  
Simple Approach ◽  
Distribution Functions ◽  
Atomic Motion ◽  
Molecular Systems ◽  
Atomic Pair ◽  
Intermolecular Distances ◽  
Supercell Model ◽  
Pair Distribution Functions ◽  
Modelling Approach

The methods currently used to calculate atomic pair distribution functions (PDFs) from organic structural models do not distinguish between the intramolecular and intermolecular distances. Owing to the stiff bonding between atoms within a molecule, the PDF peaks arising from intramolecular atom–atom distances are much sharper than those of the intermolecular atom–atom distances. This work introduces a simple approach to calculate PDFs of molecular systems without building a supercell model by using two different isotropic displacement parameters to describe atomic motion: one parameter is used for the intramolecular, the other one for intermolecular atom–atom distances. Naphthalene, quinacridone and paracetamol were used as examples. Calculations were done with theDiffPy-CMIcomplex modelling infrastructure. The new modelling approach produced remarkably better fits to the experimental PDFs, confirming the higher accuracy of this method for organic materials.

Atomic ordering in nanosized PtxAu1–x(x= 0, 0.51, 1) by resonant X-ray diffraction and differential atomic pair distribution functions

2012 ◽  
Vol 227 (5) ◽  
pp. 262-267 ◽  
Author(s):  
Valeri Petkov ◽  
Sarvjit Shastri ◽  
Bridgid Wanjala ◽  
Rameshiwori Loukrakpam ◽  
Jin Luo ◽  
...  
Keyword(s):  
Distribution Functions ◽  
X Ray Diffraction ◽  
Atomic Ordering ◽  
X Ray ◽  
Atomic Pair ◽  
Pair Distribution Functions
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