Lesson 8 Publishing XRD Results

Lesson 8 Publishing XRD Results Nicola Döbelin( s humble opinions ) RMS Foundation, Bettlach, Switzerland totally irrelevant to the rest of the world March 1 2, 216, Freiberg, Germany

Relevant Topics - Quality of Rietveld refinement results - Graphs - «Experimental» section 2 March 1 2, 216, Freiberg, Germany

Quality: Accurate + Precise https://phidgets.wordpress.com 3 March 1 2, 216, Freiberg, Germany

Quality of Rietveld Refined Data XRD / Rietveld refinements are very difficult to validate: - Often no complementary analytical technique available - Hardly any reference materials available - Refinement: Highly operator dependent One option: Participate in round robins Compare your results with other labs Round robin on CaP phase quantification organized by RMS Foundation / Nicola Döbelin in 212/213 4 March 1 2, 216, Freiberg, Germany

Quantity [%] Accuracy of Rietveld Refined Data Round Robin Reference Sample: - Simple 2 phase system: HA + β-tcp - Very homogeneous distribution - No texture 1 8 6 4 2 Volume Number - No micro-absorption - Highly crystalline.1.1 1 1 1 Particle Diameter [µm] - Mean cryst size ~2 nm Nearly «Best Case» Scenario 5 March 1 2, 216, Freiberg, Germany

Accuracy of Rietveld Refined Data Round Robin 12 Labs with 26 different instruments / configurations analyzed the same powder n=5 Results returned from one lab/instrument: Sample β-tcp [wt-%] HA [wt-%] 1 28.1 71.99 2 28.22 71.78 3 28.49 71.51 4 28.29 71.71 5 28.2 71.8 Mean (Std. Dev) 28.24 (.17) 71.76 (.17) 6 March 1 2, 216, Freiberg, Germany

HA Phase Quantity [rel. wt-%] Accuracy of Rietveld Refined Data * p <.5 ** p <.1 74 * ** 73 ** ** ND * RK * 72 * ** ** ** ** 71 ** Precise Results Accurate Results 7 A:I A:II A:IIIA:IV B:I B:II B:IIIB:IV C:I C:II D:I E:I E:II F:I G:I G:II H:I H:II H:III I:I I:II J:I J:II J:III K:I L:I M:I M:II Laboratory:Configuration Weight Fraction G:\Auftr_Proj\S-Auftraege\216\S16_4 XRD Freiberg\Abbildungen\S12_8-Mean-Values.opj Döbelin, N. "Interlaboratory study on the quantification of calcium phosphate phases by Rietveld refinement." Powder Diffraction, 215 3(3): 231-241. 7 March 1 2, 216, Freiberg, Germany

Uncertainty of Measurement Random Errors Precision Determine σ from N measurements: σ = 1 N N i=1 x i x 2 Systematic Errors Accuracy Determine Δ with reference samples Combined Uncertainty of Measurement Expanded Uncertainty of Measurement (k=2) Δ = x x reference u c = σ 2 + Δ 2 U k=2 = 2 u(c) 8 March 1 2, 216, Freiberg, Germany

HAp Refined (wt-%) Validation of β-tcp + HAp Quantification at RMS -TCP Nominal (wt-%) 1 8 6 4 2 1 8 6 Reference mixtures Hydroxyapatite + β-tcp (Whitlockite) 4 2 Measured and refined 2x 2 4 6 8 1 HAp Nominal (wt-%) 9 March 1 2, 216, Freiberg, Germany

Validation of β-tcp + HAp Quantification at RMS 1. Precision (random error) = refined - nominal (wt-%).5. -.5-1. Accuracy (systematic error) β-tcp signal drowns in counting noise = systematic error 2 4 6 8 1 HAp Nominal (wt-%) 1 March 1 2, 216, Freiberg, Germany

U(k=2) (wt-%) Validation of β-tcp + HAp Quantification at RMS 2. 1.8 1.6 1.4 1.2 1..8.6.4.2. 2 4 6 8 1 HAp Nominal (wt-%) Raynaud, S., Champion, E., Bernache-Assolant, D., and Laval, J.-P. (21). Determination of calcium/phosphorus atomic ratio of calcium phosphate apatites using X-ray diffractometry, J. Am. Ceram. Soc. 84, 359 366. Validated uncertainties of measurement compliant with ISO 1725 accreditation 11 March 1 2, 216, Freiberg, Germany

Standard Deviation (wt-%) Quality of Rietveld Refined Data.6.5 n=2 Standard Deviation Mean BGMN ESD.4.3.2.1. BGMN error propagation = very realistic estimate of σ 2 4 6 8 1 HAp Nominal (wt-%) 12 March 1 2, 216, Freiberg, Germany

Detection Limits Possible Definition of Quantification Limit (LOQ): Phase Quantity < 4 σ Possible Definition of Detection Limit (LOD): Phase Quantity < 2 σ LOQ 4σ LOD 2σ 13 March 1 2, 216, Freiberg, Germany

LOD / LOQ Warning in Profex Remember: BGMN ESDs are very realistic! 14 March 1 2, 216, Freiberg, Germany

Guidelines for Reporting Phase Quantities For error bars use 3 ESD or 2.77 ESD 3 ESD = 99.7% repeatability limit, normal distribution 2.77 ESD = 95% repeatability limit, t distribution [1] Report Values < LOQ as «< 4 ESD» Report.76 ±.23 as «<.92» Report Values < LOD as «not detected» Report.21 ±.11 as «not detected» [1] ASTM E177-13: «Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods». 15 March 1 2, 216, Freiberg, Germany

Intensity (a.u.) Intensity (a.u.) Graphs: XRD / Rietveld are «visual» methods Methods phase quantities were calculated from XRD data Is the data good enough? 1 15 2 25 3 35 4 45 5 55 Diffraction Angle ( 2 ) Your friendly reviewer 1 15 2 25 3 35 4 45 5 55 Diffraction Angle ( 2 ) 16 March 1 2, 216, Freiberg, Germany

Graphs: XRD / Rietveld are «visual» methods 2 15 Methods XRD data was analyzed by Rietveld refinement How good was the refinement? 1 5-5 -1 1 2 3 4 5 6 15 1 5 1 2 3 4 5 6 17 March 1 2, 216, Freiberg, Germany

Graphs: XRD / Rietveld are «visual» methods Recommendation: - All the information is in the raw data - Show all your raw data (documents your data quality) - Show 1 full refinement (documents your refinement quality) 15 15 - Only additional information in refinement plots (,, Bkgr): «The refinement was done right» 15 15 1 1 1 1 5 5 5 5 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 15 15 15 15 1 1 1 1 5 5 5 5 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 15 15 15 15 1 1 1 1 5 5 5 5 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 18 March 1 2, 216, Freiberg, Germany

Intensity (a.u.) Intensity (a.u.) 1 15 2 25 3 35 4 45 5 55 HA -TCP -TCP 25 C 1 C 95 C 9 C 85 C 8 C 75 C 7 C 65 C 6 C 575 C 55 C 525 C 5 C 25 C 15 1 5 1 2 3 4 5 6 15 1 5 3 31 32 33 34 35 36 b-tcp HA Graphs: XRD / Rietveld are «visual» methods Combine your raw patterns HA -TCP -TCP 25 C Diffraction Angle ( 2 ) 1 C 95 C 9 C 85 C 8 C 75 C 7 C 1 15 2 25 3 35 4 45 5 55 Diffraction Angle ( 2 ) 65 C 6 C 575 C 55 C 525 C 5 C 25 C 15 1 b-tcp HA 5 Show more graphs if the manuscript improves 3 31 32 33 34 35 36 19 March 1 2, 216, Freiberg, Germany

«Materials and Methods» Section Match the level of detail to the relevance of XRD for the study Used for phase identification - Basic intrument parameters: - Instrument / Manufacturer - Scan range (start, end, step size) - References to PDF / ICDD / COD phase entries 2 March 1 2, 216, Freiberg, Germany

«Materials and Methods» Section 21 March 1 2, 216, Freiberg, Germany

«Materials and Methods» Section Used for phase quantification - Detailed intrument parameters: - Instrument / manufacturer - Scan range (start, end, step size [ 2θ]) - Radiation, filter / monochromator, divergence slit - References to sources of crystal structures - Rietveld software (program name, version, reference) 15 1 5 1 2 3 4 5 6 22 March 1 2, 216, Freiberg, Germany

«Materials and Methods» Section 23 March 1 2, 216, Freiberg, Germany

«Materials and Methods» Section Used for advanced refinements (structural parameters, amorphous fractions, crystallite size analysis, texture analysis etc.) - Detailed intrument parameters: - Instrument / manufacturer - Scan range (start, end, step size [ 2θ]) - Radiation, filter / monochromator, divergence slit - (detector, masks, ASS, Soller slits, generator settings ) - References to sources of crystal structures - Rietveld software (program name, version, reference) - Refinement strategy - Any non-standard calculations, sample preparations, measurement conditions, etc 24 March 1 2, 216, Freiberg, Germany

«Materials and Methods» Section Refinement strategy 25 March 1 2, 216, Freiberg, Germany

«Materials and Methods» Section Special calculations 26 March 1 2, 216, Freiberg, Germany

Summary: DOs and DON Ts in Manuscripts Do: - Show your raw data (stacked plots) - Show one full refinement - Give details according to the relevance of XRD data for the manuscript Don t: - Spam the manuscript with refinement plots - Publish results from non-standard samples - Publish results from poor refinements!!! 27 March 1 2, 216, Freiberg, Germany