Lesson 2 Instrument Configurations for Profex / BGMN

Transcription

1 Lesson 2 Instrument Configurations for Profex / BGMN Nicola Döbelin RMS Foundation, Bettlach, Switzerland June 13 15, 2018, Bettlach, CH

2 Fundamental Parameters Approach 2

3 BGMN: Wavelength Distribution Geometric Instrument Data Refined Parameters (*.geq) (*.lst) Wavelength Distribution (*.lam) Diffraction Pattern Refinement Control File (*.sav) Run BGMN Refined Pattern (*.dia) Peak Parameters (*.xy) (*.par) Structure Models 1 n Refined Structures (*.str) (*.str, *.res, *.fcf, *.pdb ) 3

4 BGMN: Wavelength Distribution Charakteristic X-radiation is a physical constant. All characteristic spectra for a certain target element look the same. Values can be taken from literature. BUT: Filters change the spectrum recorded by the detector: Kbeta filter Monochromator crystal (primary or secondary beam) Digital filter (energy dispersive detector) 4

5 BGMN: Wavelength Distribution Lorentzian Curves In /Profex-BGMN-Bundle/BGMNwin/*.lam Show sub-curves 5

6 BGMN: Wavelength Distribution Lorentzian Curves Half width [1/nm] Center inverse Wavelength [1/nm] Relative Intensity ILAM = number of curves 6

7 BGMN: Wavelength Distribution 100 CuKβ CuKα 3 CuKβ CuKα 3 Intensity [a.u.] E Wavelength [Angstrom] 7

8 BGMN: Wavelength Distribution If «betaratio» is defined: Intensity = betaratio Else: Intensity =

9 When to change the *.lam file? When default Kβ / Kα 3 intensity is not correct When using a primary-beam monochromator cu_berger86.lam cu_doebelin2012.lam (= cu.lam) betaratio=

10 «Spectral Line Cursor» (S key) Default: Shows Kα 1, Kα 2, Kβ only 10

11 «Spectral Line Cursor» (S key) ILAM= *ifthenelse(ifdef(alpha3ratio),(alpha3ratio)/ ,1) % CaKa *ifthenelse(ifdef(alpha2ratio),(1-alpha2ratio)/ ,1) % CuKa1 (1) *ifthenelse(ifdef(alpha2ratio),(1-alpha2ratio)/ ,1) % CuKa1 (2) *ifthenelse(ifdef(alpha2ratio),(alpha2ratio)/ ,1) % CuKa2 (1) *ifthenelse(ifdef(alpha2ratio),(alpha2ratio)/ ,1) % CuKa2 (2) *ifthenelse(ifdef(betaratio),(betaratio)/ ,1) % CuKb Trailing comment = label Lines without comment will not be shown 11

12 BGMN: Geometric Instrument Data Geometric Instrument Data Refined Parameters (*.geq) (*.lst) Wavelength Distribution (*.lam) Diffraction Pattern Refinement Control File (*.sav) Run BGMN Refined Pattern (*.dia) Peak Parameters (*.xy) (*.par) Structure Models 1 n Refined Structures (*.str) (*.str, *.res, *.fcf, *.pdb ) 12

13 BGMN: Geometric Instrument Data Profile Interpolation Raytraced Peak Profiles (*.ger) Monte-Carlo Simulations Geometric Instrument Data (*.geq) Wavelength Distribution (*.lam) Diffraction Pattern (*.xy) Refinement Control File (*.sav) Instrument Description (*.sav) Structure Models 1 n (*.str) 13

14 BGMN: Geometric Instrument Data Profile Interpolation Geometric Instrument Data (*.geq) Raytraced Peak Profiles (*.ger) Monte-Carlo Simulations Instrument Description (*.sav) 14

15 BGMN: Geometric Instrument Data 3 things required 15

16 BGMN: Geometric Instrument Data 1. Physical access to the instrument and technical documentation 16

17 BGMN: Geometric Instrument Data 2. Access to the control software 17

18 BGMN: Geometric Instrument Data 3. A reference dataset - Reference sample (e.g. NIST SRM) - Measured with the instrument configuration to be used with Profex - Measured over a wide angular range (e.g ), wider than future standard measurements 18

19 BGMN Variables 19

20 BGMN: Geometric Instrument Data Open existing instrument *.sav file Choose one that resembles your configuration (same manufacturer, same detector, variable or fixed divergence slit) Change / add / remove variables Run raytracing and interpolation Go through the file line by line If your instrument has the optical element but you don t know the setting, leave it at the default If your instrument doesn t have this element, remove (or comment) the line If your instrument has additional elements, add them according to the schematic no Test config by refining ref. dataset Result ok? yes Done Difference curve must be nearly perfect Crystallite sizes must be realistic (compare with SRM certificate) Practical examples after lunch 20

21 BGMN: Geometric Instrument Data Open existing instrument *.sav file Change / add / remove variables Run raytracing and interpolation Test config by refining ref. dataset no Result ok? yes Done 21

22 BGMN: Geometric Instrument Data Open existing instrument *.sav file Change / add / remove variables Run raytracing and interpolation Test config by refining ref. dataset no Result ok? yes Done 22

23 Verification with SRM NIST SRM 1976b Al 2 O 3 The platelets were typically 5 μm to 10 μm in diameter by 2 μm to 3 μm in thickness This leads to a minimal development of micro-strain and its associated line broadening Given this, and the essential absence of crystallite size broadening, SRM 1976b can be used to obtain an approximation of the instrument profile function (IPF) 23

24 NIST Standard Reference Materials (SRM) 24

25 Non-standard configurations What about: - Primary beam monochromators - Area detectors - Synchrotron / neutron diffractometers - Future optics Fake the configuration until the peak profile matches Or use Profex with FullProf 25

26 Faked Instrument Configurations We need to get there No matter how 26

27 Faked Instrument Configurations Aligned instrument Misaligned instrument Anti-Scatter Slit Divergence Slit Anti-Scatter Slit Divergence Slit Beam Shape Beam Shape H H W W 27

28 Exercises Exercise 1: Configure the RMS standard instrument setup, starting from a totally wrong template. Exercise 2: Configure an instrument with a primary beam monochromator. (Nobody has succeeded yet ) 28