4.   Special Display Interfaces


SuperPlot - Overplotting | Scaling and Zooming | Cut applied to ... | Plot Style and Printing | Tips
Radial integrations
Unroll images
Curve fit - Str-Fit(complete and generous) | GK-Fit(limited but easy to use | Qens-Fit(for quasi-elastic spectra)
Tomography
Magnetic structure - Editor | incommensurate example | commensurate example
Atomistic representation - Miller planes/isodensities | Molecules/displacements
Scroll Spectra - Scrolling | Scaling and Zooming | Plot Style and Printing | Tips


The DISPLAY FUNCTIONS list on the right of the classical LAMP interface and the TOOLS list in the Menu-bar contain buttons to select the following interfaces :-

SuperPlot

This interface provides a window for plotting several individual spectra. The current workspace number used in Lamp is automatically used as the default workspace. You can change it with the workspace slider. The cut axis and the cutting value can also be easily choosen using X or Y button and cutting value slider.

The SuperPlot window diplaying five spectra from 1 workspace
[Snapshot]


Also in the DISPLAY FUNCTIONS area on the right of the main LAMP interface are buttons to select a Radial Integration programs, a curve function fitting program (GK_Fit), SCAN for more elaborate image manipulation, and Load new Colours.



RADIAL INTEGRATIONS

This interface provides a window for radial and azimutal integrations using user defined sectors.



UNROLLING RINGS

This interface provides a window for unrolling large images.The analyse becomes easier since integrations are simple projections.




CURVE FITTING with Str_Fit

Originally developed for analysing strain scanning aquisitions in which a Bragg peak is measured as a function of the position in the sample. The diffraction peak in each pattern is fitted with a given theorical lineshape (e.g. pseudo-Voigt), including convolution with a resolution function.
The fitted data, residuals and parameters can be viewed in different ways.
Today the program aims to give users a general fitting interface in which we can:

  • Construct a model by entering own formulae and using predefined functions.
  • Constraint and tie parameters for independent spectra or 2D spectra (simultaneous fitting).
  • Fit parameters in one go using previous spectra results.
  • Choose a resolution as a function or numerical input spectra.
  • Save models and results. Call "Str_fit" from a macro without using the interface.


  • CURVE FITTING with GK_Fit

    From one to six Gaussian & Lorenzian functions can be fitted from this interface.


    CURVE FITTING with Qens_Fit

    Used to analyse quasi-elastic spectra. Inelastic excitations can also be treated. The input for "Qens_fit" consists of two workspaces, one containing the data as a function of Q(or temperature,pressure etc), the other containing the corresponding set of resolution functions, and a fitting model(typically a delta function for the elastic peak and lorentzians and gaussians for the quasi/inelastic features).
    Once one spectrum has been fitted the remaining spectra can be fitted in one go and parameters can be fixed for all spectra. Instead of fitting independently each spectrum, a physical model can be imposed, for example for diffusion on a sphere. Models are added when needed.


    TOMOGRAPHY

    A straightforward interface for reconstruction.


    MAGNETIC STRUCTURE

    An editor for magnetic strutures representations with the possibility to add planes and do animations. MAGDRAW reads the nuclear and magnetic structures following Rietvelt refinement in standard programs like "FULLPROF". The structure is displayed as a 3D object that can be easily rotated.


    DyMn6Ge6 incommensurate magnetic structure in MAGDRAW. The magnetic structure is characterized by two propagation vectors K1=(0,0,0) and K2=(0,0,.16). the first one provides a ferro-magetic component to the helical part described in K2.


    Cu4O3 commensurate magnetic structure in MAGDRAW

    MILLER PLANES, ISOSURFACE OF ELECTRON OR SPIN DENSITY

    Miller planes can be shown in the crystallographic cell to help visualise local structure. Standard representations of atoms and structural units(balls,sticks,polyhedra etc) are available. High quality images and animations can be saved for publications or presentations.
    Atomistic representations are also being explored for visualising the results of solid state, first principles calculations on materials. Computational codes like VASP based on density functional theory (DFT), allow electron and spin density to be calculated and these can be displayed with the crystal structure.

    3D isosurface and 2D contour plot representations of electron density, calculated by VASP for LiFePO4.

    MOLECULES/DISPLACEMENTS

    The animation capabilities in LAMP can be used to visualise molecular dynamics simulations and calculated phonons and molecular vibrations.


    Scroll Spectra

    This provides a window for scrolling through the individual spectra within a workspace. At start-up only triangles are displayed until an input workspace is selected using Load W#.

    The Scroll Spectra window diplaying just two spectra from a workspace
    [Snapshot]



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