Changes between Initial Version and Version 1 of Tutorials/Swedness/Lab1C

Timestamp:

Aug 22, 2018 3:39:23 AM (6 years ago)

Author:

ajj

Comment:

—

Tutorials/Swedness/Lab1C

@@ +1 @@
+= KEMM37 Lab 1B - SANS Data Analysis using !SasView =
+
+||= **Table of Contents** =||
+|| [#section5 5. Fitting SANS data] ||
+||   [#section51 5.1 Background Information] ||
+||   [#section52 5.2 Calculating Scattering Length Density] ||
+||   [#section53 5.3 Fitting the data] ||
+|| [#resources Resources] ||
+
+== [=#section5 5. Fitting SANS data] ==
+
+This part of the exercise will use the same real SANS data as the previous exercises - taken from a study of surfactant self assembly in deep eutectic solvents (DES). 
+
+{{{
+#!div style="background: lightblue"
+[=#task10 **TASK 10:**] Restart !SasView
+
+Before starting this part of the exercise, you should have a clean !SasView instance. Quit !SasView and restart it.
+}}}
+
+=== [=#section51 5.1 Background Information] ===
+Deep 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.
+
+Here 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].
+
+||Sodium Dodecyl Sulfate||Choline Chloride||Urea||
+||[[Image(kemm37_sds.png)]]||[[Image(kemm37_choline.png)]]||[[Image(kemm37_urea.png)]]||
+
+{{{
+#!div style="background: lightblue"
+[=#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.
+}}}
+
+You should now have a folder called "Subtracted" containing a set of files named as follows:
+
+[[Image(kemm37_datafileslist.png)]]
+
+The 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:
+
+|| Surfactant Concentration (wt%) || Data File ||
+|| 0.2 || 0p2hSDS_dChCldUrea_sub.txt ||
+|| 0.5 || 0p5hSDS_dChCldUrea_sub.txt ||
+|| 1.0 || 1hSDS_dChCldUrea_sub.txt ||
+|| 2.0 || 2hSDS_dChCldUrea_sub.txt ||
+|| 5.0 || 5hSDS_dChCldUrea_sub.txt ||
+|| 7.5 || 7p5hSDS_dChCldUrea_sub.txt ||
+|| 10.0 || 10hSDS_dChCldUrea_sub.txt ||
+
+All 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.
+
+Additionally there is a folder called "Not subtracted" containing the data for task 14.
+
+=== [=#section52 5.2 Calculating Scattering Length Density] ===
+
+The scattering length density is given by 
+
+[[Image(kemm37_sld.png, 100px)]]
+
+Scattering lengths of relevant elements:
+||= **Element** =||= **Scattering Length (fm)** =||
+||C     ||6.646||
+||H     ||-3.739||
+||D     ||6.671||
+||N     ||9.36||
+||O     ||5.803||
+||Cl    ||9.577||
+
+
+Physical properties of the DES components:
+||= **Component**       =||= **Chemical Formula** =||=  **Molecular Volume (Å3)**       =||= **Density (g/cm3)** =||
+||d9-Choline Chloride|| C5H5D9NOCl      ||  210.77||  1.17||
+||d4-Urea||     CD4N2O  ||   75.55||    1.41||
+
+
+{{{
+#!div style="background: lightblue"
+[=#task12 **TASK 12:**] Calculate the scattering length density (SLD) of a 1:2 mole ratio mixture of choline chloride and urea.
+
+Use the information in the table above to calculate the SLD. There are multiple ways to do so, including:
+* Calculating by hand
+* Using a spreadsheet
+* Using the SLD calculator built in to !SasView (in the Tools menu).
+* Using online calculators e.g. [https://www.ncnr.nist.gov/resources/activation/]
+
+Try calculating by hand and one or more of the other ways and see if you get the same answer!
+}}}
+
+
+=== [=#section5. 5.3 Fitting the data] ===
+{{{
+#!div style="background: lightblue"
+[=#task19 **TASK 19:**] Fitting the lowest concentration data.
+
+Select 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.
+
+* Select the model for the structure you predicted for this dataset. 
+  * How does it compare to the data?
+* Fill in parameters you know and adjust the others to see how close you get to the data.
+* Select parameters to fit and run the fit by clicking "Fit" at the bottom of the fitting panel.
+  * Do you get a good fit?
+  * Are the parameters you get physically reasonable?
+
+}}}
+
+
+{{{
+#!div style="background: lightblue"
+[=#task20 **TASK 20:**] Fitting the other data, starting with the 7.5 wt% data set.
+
+Repeat for other concentrations
+* Does the same model fit all data?
+* What is consistent between datasets? What is different? 
+
+
+}}}
+
+{{{
+#!div style="background: lightblue"
+[=#task21 **TASK 21:**] Summarising the results
+
+Having fitted all the data sets you can now summarise the results and comment on the trends you observe.
+
+}}}
+
+
+== [=#resources Resources] ==
+
+* NIST SLD calculator [https://www.ncnr.nist.gov/resources/activation/]
+* NIST Scattering Length and Scattering Cross Section Database [https://www.ncnr.nist.gov/resources/n-lengths/]