Ovidiu Garlea. Neutron Scattering Sciences Division Oak Ridge National Laboratory

Transcription

1 Ovidiu Garlea Neutron Scattering Sciences Division Oak Ridge National Laboratory based on materials presented by Juan Rodríguez-Carvajal Institute Laue-Langevin, Grenoble

2 Juan Rodríguez-Carvajal (ILL, LLB, France) CrysFML, FullProf, BasIreps, Simbo, Enermag, Polar3D, Javier González-Platas (ULL, Tenerife, Spain) CrysFML, GUIs, GFourier, EdPCR Contributors: Thierry Roisnel (LCSIM, Rennes, France): WinPLOTR Oscar Baltuano (IPEN, Peru): WinPLOTR-2006 Carlos Frontera (ICMAB, Barcelona, Spain): Polarized neutrons Marc Janoschek (PSI, Villigen, Switzerland) 3D-Polarimetry Laurent Chapon & Aziz Daoud-Aladine (ISIS, U.K.) T.O.F., FP_Studio 2 Managed by UT-Battelle

3 3 Managed by UT-Battelle

4 4 Managed by UT-Battelle

5 A set of crystallographic programs (FullProf, WinPLOTR, EdPCR ) developed for Rietveld analysis of neutron or X-ray powder diffraction, but with capabilities for single crystal and having many useful utilities 5 Managed by UT-Battelle

6 6 Managed by UT-Battelle

7 FP_Suite_Toolbar: Program for accessing the whole set of the FullProf Suite. WinPLOTR / WinPLOTR-2006: Programs for visualizing powder diffraction patterns. Fitting independent peaks (CW and TOF), interface for FullProf FullProf : Crystal and magnetic structure refinement, powder/single crystals, polarized neutrons, multiple patterns, simulated annealing EdPCR: Editor of the FullProf input control file GFourier and Bond_Str.: Fourier and distance/angle calculations. SuperCell/K_Search: Searching propagation vectors BasIREPS: Program for calculating basis functions of irreducible representations of space groups. Fp_Studio: Program for visualizing crystal and magnetic structures Check_Group: Program for finding the space group (powders and single crystals) Datared/GDatared: Program for single crystal data reduction Mol_tpcr: console utility for creating Rigid body groups External programs: DICVOL04, TREOR90, ITO, XLENS 7 Managed by UT-Battelle

8 Program to visualize the diffraction patterns Reading the X-ray and neutron diffraction patterns Automatic peak search for indexing Saving peaks as DICVOL04, Treor90, K-Search... Running indexing programs Automatic generation of PCR file for cell refinement and integrated intensity extraction Making individual peak fit Exporting a background file Invoking other programs (can access the whole FullProf Suite) 8 Managed by UT-Battelle

9 Access to other programs: (e.g., periodic table of elements, space groups info, molecular weight and unit cell volume calculation ) Individual peak fit Automatic peak & background search 9 Managed by UT-Battelle

10 Search for the magnetic propagation vector (k-search) 2D contour plot 3D surface plot 10 Managed by UT-Battelle

11 A program for : Simulation of powder diffraction patterns Pattern decomposition integrated intensities Crystal and magnetic structure refinement Powder and single crystal data Structure determination capability: Simulated annealing on integrated intensity data Flipping ratio refinements 11 Managed by UT-Battelle

12 Program features include: Multiple data sets: simultaneous treatment of several powder diffraction patterns (CW X-rays & neutrons, Energy dispersive X-rays, TOF neutron diffraction) Combined treatment of single crystal and powder data Automatic mode for handling refinement codes and symmetry constraints Rigid body refinements + distances and angles restraints Special form factors The treatment of micro-structural effects Sequential refinement 12 Managed by UT-Battelle

13 Documented in fp2k.inf or to the Fullprof homepage at What s new 13 Managed by UT-Battelle

14 14 Managed by UT-Battelle

15 Minimal input: Input control file (extension.pcr ): PCR-file Model, crystallographic / magnetic information, Experimental parameters Eventually, experimental data (Format depending on the instrument) 15 Managed by UT-Battelle

16 Many variables and options Complex to handle Hint: copy an existing PCR-file and modify it for the user case, or... USE the GUI: EdPCR 16 Managed by UT-Battelle

17 Imports crystal structures from CIF and SHELX files Constraints: reduce the number of free parameters (rigid body refinements) Restraints: same number of free parameters + additional observations 17 Managed by UT-Battelle

18 18 Managed by UT-Battelle

19 19 Managed by UT-Battelle Let's get specific!

20 Modeling the entire diffraction pattern For unpolarized neutrons: ci h i h i h y I ( T T ) b I h N h N * h M h M * h M h e M(h) e M(h) e (e M(h)) LaMnO 3 : 50K and 150 K Complete structural model should be provided 20 Managed by UT-Battelle

21 m magnetic moment expanded as Fourier series ljs k S k exp 2 ikr js l : index of a direct lattice point j : index for a Wyckoff site (orbit) s: index of a sublattice of the j site The magnetic structure factor: l S kjs : Fourier coefficients are complex vectors 1 Sk ( Rk iik )exp{ 2 i k } 2 at the origin : m = S k Necessary condition for real moments kjs kjs S - S n po f T 2 k exp i S M h h S H k t r s j1 S j j j js j s t s Symmetry operators 21 Managed by UT-Battelle

22 two different ways of treating magnetic structures: The magnetic symmetry is introduced together with explicit symmetry operators of the crystal structure. The refined variables are directly the components of the S kjs vectors. A relation exist between. S kj1 and S kjs S M S exp i kjs js kj1 2 kj Fourier coefficients as linear combinations of the basis functions of the irreducible representation of the propagation vector group G k S C k kjs n n n The basis functions of the IRs are introduced together with explicit symmetry operators of the crystal structure. The refined variables are directly the coefficients C 1, C 2, C 3,. S js 22 Managed by UT-Battelle

23 Magnetic phase!!nat Dis Mom Pr1 Pr2 Pr3 Jbt Irf Isy Str Furth ATZ Nvk Npr More ! P m m m <--Space group symbol!nsym Cen Laue MagMat ! SYMM x,y,z MSYM u,v,w,0.0 SYMM -x,-y,z+1/2 MSYM -u,-v,w,0.0 SYMM -x+1/2,y+1/2,-z+1/2 MSYM u,-v,w,0.0 SYMM x+1/2,-y+1/2,-z MSYM -u, v,w,0.0!!atom Typ Mag Vek X Y Z Biso Occ Rx Ry Rz! Ix Iy Iz beta11 beta22 beta33 MagPh Mn1 MMN Managed by UT-Battelle

24 !Nat Dis Mom Pr1 Pr2 Pr3 Jbt Irf Isy Str Furth ATZ Nvk Npr More ! P m m m <--Space group symbol! Nsym Cen Laue Ireps N_Bas ! Real(0)-Imaginary(1) indicator for Ci 0 0 0! SYMM x,y,z BASR BASI SYMM -x+1,-y,z+1/2 BASR BASI SYMM -x+1/2,y+1/2,-z+1/2 BASR BASI SYMM x-1/2,-y+1/2,-z BASR BASI !!Atom Typ Mag Vek X Y Z Biso Occ C1 C2 C3! C4 C5 C6 C7 C8 C9 MagPh Mn1 MMN Managed by UT-Battelle

25 25 Managed by UT-Battelle more specific

26 I. Well defined crystallographic structure model (FullProf) II. Determine the propagation vector(s) (k-search) Peak positions of magnetic reflections Cell parameters III. Perform Symmetry Analysis (BasIreps) IV. Introduce and refine by LSQ the magnetic phase (FullProf) for more complicated structures Structure solution Simulated annealing (FullProf) Propagation vector Space Group Atom positions Atomic components of basis functions Extracted integrated intensities 26 Managed by UT-Battelle

27 Extract ' I ( T T )( y B ) i k obs, i i obs, k ' Icalc, k i ( ycalc, i Bi ) (Profile matching) Minimize the difference between the observed and the calculated integrated intensities against the parameter vector I M w ( G G ( )) n n obs, n calc, k I k use spherical components of Fourier coefficients better control of the amplitude Constraint the obtained models (representation analysis) Refine them back the with the Rietveld method 27 Managed by UT-Battelle

28 28 Managed by UT-Battelle

29 BasIreps provides the basis functions (normal modes) of the irreducible representations of the wave-vector group G k Code of files Title k-vector Axial/polar Number of atoms 29 Managed by UT-Battelle Working directory Space group symbol or generators Brillouin Zone label Atoms in Unit Cell Atoms positions

30 Format for FullProf k=(0,0,0), =1, n=1,2,3 =1, j=1, s=1,2,3,4 k S n js 30 Managed by UT-Battelle

31 31 Managed by UT-Battelle visualising crystal and magnetic structures input file has the extension ".fst" and it is automatically generated by FullProf after a structure refinement

32 Examples and tutorials can be found in the Web page of the FullProf Suite at ILL 32 Managed by UT-Battelle