Indira Gandhi Centre for Atomic Research, India GBgeom - Manual T. Karthikeyan, Indira Gandhi Centre for Atomic Research, India 10-May-2013

GBgeom Program Outputs Four types of graphical windows for: User Input Screen Crystal Orientation and Texture Parameters EBSD Experiment Set-up and Kikuchi Pattern Construction Geometry of Atomic Structure at the Grain Boundary Plane

Program Controls User input interface is through the keyboard Information regarding the input options are described contextually in the input screen Various options for program control (including the button key to change over to a different screen) are listed within each window output

Functions of ‘GBgeom’ program

Functions of ‘GBgeom’ program User Input Screen To declare the initial user inputs such as, Crystal type (BCC/FCC) Grain boundary parameter input based on Coherent Coincidence Site Lattice (or) (S3,5,7,9,11,13a,13b,15,17a,17b,19a,19b,21a,21b,23,25a,25b,27a,27b,29a,29b) User defined values of the Two grains orientations (in Euler angles) & Grain boundary inclination (Azimuth, polar angle)

Functions of ‘GBgeom’ program Crystal Orientation & Texture Parameter Window To depict orientation parameters and the various texture attributes in cubic crystals such as the: Euler angles Pole positions (of [100]/[110]/[111]) in planar, stereographic and equal area projections Inverse poles of the sample directions (X/Y/Z) Single step rotation axes – rotation angle Drawing of unit cell orientation in the specimen and Demonstration of the individual steps of Euler rotations

Functions of ‘GBgeom’ program Crystal Orientation & Texture Parameter Window To illustrate the effect of cubic crystal symmetry by Depiction of 24 equivalent points in Euler parametric space and the reduced domains and Representation of the 24 equivalent single step rotation axes in a pole figure and display the minimum misorientation angle-axis To perform and animate systematic rotations based on users choice of rotation axis and step-angle to graphically illustrate the Underlying relations between change in Euler angle, crystal orientation, crystallographic & sample directions and the misorientation axis

Functions of ‘GBgeom’ program EBSD Set-up & Kikuchi Pattern Window To draw the typical sample, detector screen geometry of the EBSD experiment set-up in a perspective projection To show the Spherical Kikuchi map construction of the prominent diffracting planes (for Iron system), for the specific instance of crystal orientation To illustrate the gnomonic projection of the crystal plane trace on the rectangular detector screen (for a typical experimental settings) to arrive at the expected geometry of the EBSD pattern

Functions of ‘GBgeom’ program Grain Boundary Geometry Window To depict the unit cell orientations of the adjoining crystals and the associated misorientation angle-axis between them using pole projections To depict the oblique inclination of grain boundary plane & its trace line in the sample plane To denote the type of crystallographic planes for the two crystals meeting at the grain boundary interface

Functions of ‘GBgeom’ program Grain Boundary Geometry Window To depict the basic un-relaxed atomic positions of the adjoining cubic crystals at the grain boundary plane, by assuming a common shared point at the origin To illustrate the nature of misfit and visually bring-out the possible ordered structure at the grain boundary plane by displaying Lattice positions lying closer to the GB plane Wigner-Seitz cell for the two orientations Polygons got by intersection of grain boundary plane with W-S cells of the two crystals

Functions of ‘GBgeom’ program Grain Boundary Geometry Window To systematically change the grain boundary inclination (by changing polar/azimuth angle of GB pole) To view the atomic structure at the oblique grain boundary plane at different length scales by zooming in/out control options To depict the flat projection of the atomic structure of grain boundary plane

‘GBgeom’ Usage

Usage: User Input Screen Input values of crystal type & boundary parameters are typed in sequentially Valid numerical values typed and entered to accept (& similarly for other above inputs) Finally, typing of ‘S’ takes the program to grain boundary simulation screen

Usage: User Input Screen Input screen in case of a CSL type of grain boundary Values of Euler angles for the two grains are such that the coherent twin plane (of the chosen CSL) is aligned with the sample surface

Usage: Crystal Orientation & Texture Parameter Window Screenshot of the program depicting the different texture parameters and attributes Changing step rotation angle between (-10°,-1°,-0.1°,0°,0.1,1°,10°) Mode of step rotations: C/P Selection of rotation axis options: 0-6 To alter to the other window S: to select the chosen orientation and move to next screen K: to move to the Kikuchi pattern window

Usage: EBSD Set-up & Kikuchi Pattern Window To visualize more or less number of HKL plane traces To go back to the crystal orientation & texture parameter window Screenshot showing the geometrical construction of EBSD Kikuchi pattern distribution

Usage: Grain Boundary Geometry Window Screenshot showing the simulated structure of a symmetrical grain boundary with 8° deviation from ideal S3 in FCC changing GB inclination by step-rotations Mode of step rotations: C/P Type of angle to be changed: A/T Choices for displaying GB attributes: E,W,L To view at different length scale: I/O To change to other windows: F- GB Flat view U- User input 1/2: Texture parameters of the two crystals

Usage: Grain Boundary Geometry Window Screenshot showing the simulated structure in a BCC grain boundary for arbitrary set of Euler angles and grain boundary inclination angles To go back to the window showing oblique view of the grain boundary structure

Usage: Grain Boundary Geometry Window Screenshot showing the simulated structure in a BCC grain boundary for arbitrary set of Euler angles and grain boundary inclination angles D: To export grain boundary parameter data to “Data.dat” file Q: To exit the program

Usage Screen output can be conveniently captured by the user with the standard ‘Print Screen’ keyboard button to copy the screen image and transfer it to image processing programs. Grain orientations and grain boundary parameters for specific instances of GB structure can be selectively stored by user to a text file (‘Data.dat’). Program terminated through ‘Q’ key in the GB geometry window

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