Changes between Initial Version and Version 1 of Tutorials/Swedness/Lab1B


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Aug 22, 2018 5:32:24 AM (6 years ago)
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ajj
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  • Tutorials/Swedness/Lab1B

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     1= KEMM37 Lab 1B - SANS Data Analysis using !SasView = 
     2 
     3||= **Table of Contents** =|| 
     4|| [#section4 4. Rapid Evaluation of SANS data] || 
     5||   [#section31 4.1 Background Information] || 
     6||   [#section42 4.2 Evaluation of the SANS data] || 
     7|| 
     8 
     9== [=#section4 5. Rapid Evaluation of SANS data] == 
     10 
     11This part of the exercise will use the same real SANS data as the last exercise - taken from a study of surfactant self assembly in deep eutectic solvents (DES).  
     12 
     13{{{ 
     14#!div style="background: lightblue" 
     15[=#task10 **TASK 10:**] Restart !SasView 
     16 
     17Before starting this part of the exercise, you should have a clean !SasView instance. Quit !SasView and restart it. 
     18}}} 
     19 
     20=== [=#section41 4.1 Background Information] === 
     21Deep eutectic solvents are a class of ionic liquids formed from a hydrogen bond donor and a halide salt. At a certain mixture ratio, the eutectic mixture, the melting point is significantly depressed to values below room temperature. 
     22 
     23Here we will examine the self-assembly of a [https://en.wikipedia.org/wiki/Surfactant surfactant], [https://en.wikipedia.org/wiki/Sodium_dodecyl_sulfate sodium dodecyl sulfate (SDS)] in the deep eutectic solvent formed from a 1:2 molar ratio mixture of [https://en.wikipedia.org/wiki/Choline_chloride   choline chloride] and [https://en.wikipedia.org/wiki/Urea   urea]. 
     24 
     25||Sodium Dodecyl Sulfate||Choline Chloride||Urea|| 
     26||[[Image(kemm37_sds.png)]]||[[Image(kemm37_choline.png)]]||[[Image(kemm37_urea.png)]]|| 
     27 
     28{{{ 
     29#!div style="background: lightblue" 
     30[=#task11 **TASK 11:**] If you haven't already done so, download the SANS data :  [attachment:SwednessSasViewTutorialData.zip​] and unzip the file in a known location on your filesystem. Note where you have placed the data. 
     31}}} 
     32 
     33You should now have a folder called "Subtracted" containing a set of files named as follows: 
     34 
     35[[Image(kemm37_datafileslist.png)]] 
     36 
     37The data are SANS curves collected on SANS2D at ISIS and D22 at ILL for samples of protonated (normal) SDS in 1:2 d9-choline chloride:d4-urea. This sample was chosen to give maximum contrast and minimum background signal from incoherent scattering. There were 7 samples with 0.2 wt%, 0.5 wt%, 1.0 wt%, 2.0 wt%, 5.0 wt%, 7.5 wt% and 10 wt% of SDS in the DES with the filenames corresponding to each sample given below: 
     38 
     39|| Surfactant Concentration (wt%) || Data File || 
     40|| 0.2 || 0p2hSDS_dChCldUrea_sub.txt || 
     41|| 0.5 || 0p5hSDS_dChCldUrea_sub.txt || 
     42|| 1.0 || 1hSDS_dChCldUrea_sub.txt || 
     43|| 2.0 || 2hSDS_dChCldUrea_sub.txt || 
     44|| 5.0 || 5hSDS_dChCldUrea_sub.txt || 
     45|| 7.5 || 7p5hSDS_dChCldUrea_sub.txt || 
     46|| 10.0 || 10hSDS_dChCldUrea_sub.txt || 
     47 
     48All the data files have been processed to 1D scattering curves with the solvent background subtracted to leave only the coherent scattering signal on absolute scale. 
     49 
     50Additionally there is a folder called "Not subtracted" containing the data for task 14. 
     51 
     52=== [=#section42 4.2 Evaluation of the subtracted data] === 
     53 
     54You will now load the background subtracted data into !SasView and make a plot in order to visually inspect the scattering curves.  
     55 
     56If you are continuing directly from the first part of the exercise - "Familiarisation with SasView and Data Handling" you can skip to TASK 18, otherwise start with TASK 15. 
     57 
     58{{{ 
     59#!div style="background: lightblue" 
     60[=#task15 **TASK 15:**] Restart !SasView 
     61 
     62Before starting this part of the exercise, you should have a clean !SasView instance. Quit !SasView and restart it. 
     63}}} 
     64 
     65{{{ 
     66#!div style="background: lightblue" 
     67[=#task16 **TASK 16:**] Click on the "Load Data" button in the Data Explorer 
     68 
     69Locate the folder where you placed the data, select all the files in the "subtracted" folder and click "Open" in the dialog. 
     70}}} 
     71 
     72The Available Data section of the Data Explorer should look something like: 
     73 
     74[[Image(kemm37_loaddata.png)]] 
     75 
     76 
     77{{{ 
     78#!div style="background: lightblue" 
     79[=#task17 **TASK 17:**] Plot the loaded data 
     80 
     81Make sure that all the datasets have check marks next to them in the Available Data section of the Data Explorer, as shown above. 
     82 
     83Click the "New Plot" button in the Data Explorer. 
     84}}} 
     85 
     86A new window should appear with a plot of the data that looks something like: 
     87 
     88[[Image(kemm37_dataplot.png)]] 
     89 
     90{{{ 
     91#!div style="background: lightblue" 
     92[=#task18 **TASK 18:**] Examining the Data. 
     93 
     94Visually inspect the data, zooming in and making additional plots as needed. 
     95 
     96* What trends do you notice? 
     97* What can you say about the possible solution structure from looking at the data? 
     98 
     99}}} 
     100 
     101 
     102 
     103 
     104=== [=#section35 3.5 Fitting the data] === 
     105{{{ 
     106#!div style="background: lightblue" 
     107[=#task19 **TASK 19:**] Fitting the lowest concentration data. 
     108 
     109Select the lowest concentration data only in the data explorer by ensuring only 0p2hSDS_dChCldUrea_sub.txt has a check mark next to it and click “Send to" fitting. 
     110 
     111* Select the model for the structure you predicted for this dataset.  
     112  * How does it compare to the data? 
     113* Fill in parameters you know and adjust the others to see how close you get to the data. 
     114* Select parameters to fit and run the fit by clicking "Fit" at the bottom of the fitting panel. 
     115  * Do you get a good fit? 
     116  * Are the parameters you get physically reasonable? 
     117 
     118}}} 
     119 
     120 
     121{{{ 
     122#!div style="background: lightblue" 
     123[=#task20 **TASK 20:**] Fitting the other data, starting with the 7.5 wt% data set. 
     124 
     125Repeat for other concentrations 
     126* Does the same model fit all data? 
     127* What is consistent between datasets? What is different?  
     128 
     129 
     130}}} 
     131 
     132{{{ 
     133#!div style="background: lightblue" 
     134[=#task21 **TASK 21:**] Summarising the results 
     135 
     136Having fitted all the data sets you can now summarise the results and comment on the trends you observe. 
     137 
     138}}} 
     139 
     140== What's Next? == 
     141 
     142You can now move on to finishing your lab report - details are here : [wiki:KEMM37/Report KEMM37 Lab 1 Report] 
     143 
     144== [=#resources Resources] == 
     145 
     146* NIST SLD calculator [https://www.ncnr.nist.gov/resources/activation/] 
     147* NIST Scattering Length and Scattering Cross Section Database [https://www.ncnr.nist.gov/resources/n-lengths/]