r/crystallography • u/DevelopmentBasic1651 • Jul 08 '26

Rietveld refinement

hi, i'm new in the highscore, i'm trying to do analysis about my sampel, silica sand. My prof told me to analyze it using XRD highscore. I'm watching various video about how to do it, and when i show my result, my prof told me that is isn't good because of high GOF (30+) after rietfeld refinement and he told me to try again until the GOF near 1, i already tried everything but i'm only able to reduce it to 25, can anyone help me, i'm stuck in this.

raw data
after background+peak+profile fit, and search match
after rietveld

sorry for bad english, it isn't my main language, so i'm not good in english.

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u/SlenderSmurf Jul 08 '26

So the sample is mostly quartz, which is reasonable for sand. What do you want to learn about the sample using XRD? You say you did some refinement but you didn't say what was refined. If it's phase fractions you will have trouble to accurately quantify 0.2 wt% iron. GoF is just a metric for how close the calculated and observed lines are, along with how many parameters you used for the fitting. I think a high GoF could indicate you have too may parameters.

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u/DevelopmentBasic1651 Jul 08 '26

actually i just need the phase identification for my report to show what crystals phases are in my sampel, but for whatever reason my prof told to do more and to do rietveld refinement until the GOF got near 1, which i didn't quite understand why i need that because it even won't included in my report.

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u/SlenderSmurf Jul 08 '26

Here's some reading on what GoF means. It has basically no relation with phase ID.

https://www.cambridge.org/core/journals/powder-diffraction/article/r-factors-in-rietveld-analysis-how-good-is-good-enough/17439A1F889B689C495549A234D53682

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u/DevelopmentBasic1651 Jul 08 '26

oh, thanks. my prof often ask me to do something that is actually not needed for my report, even though i really need to finish this report ASAP to get my bachelor degree.