Materials Algorithms Project
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Program MAP_CRYSTAL2_PROGRAM

Provenance of code.
Purpose of code.
Specification.
Description of subroutine's operation.
References.
Parameter descriptions.
Error indicators.
Accuracy estimate.
Any additional information.
Example of code
Auxiliary subroutines required.
Keywords.
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Provenance of Source Code

Sree Harsha Lalam and H.K.D.H. Bhadeshia,
Phase Transformations Group,
Department of Materials Science and Metallurgy,
University of Cambridge,
Cambridge, U.K.

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Purpose

An interactive program for analysis of electron diffraction patterns. Program 'test_precipitates.c' requires data from a file 'ppt.dat'. This latter file contains a list of possible crystal structures against which electron diffraction data are compared. The program test_precipitates.c also calls the program 'crystal_new.for' to do the analysis. The complete program, is ready for compilation. A form compiled for LINUX is also available for downloading.

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Specification

Language:	C and FORTRAN
Product form:	Source code and compiled LINUX executable.

This is a self-contained program.

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Description

The program needs inputs from the user :-

1) The possible precipitates has to be selected in the data file 'ppt.dat'. The program is written for the crystal structures 'CUBIC, FCC, HEXAGONAL, ORTHORHOMBIC and TETRAGONAL' only. The format of 'ppt.dat' file is;

TYPE                      CODE          a               b      c               PRECIPITATE         POSSIBLE_OR_NOT
HEXAGONAL         3              2.888           0      4.559        (Cr,Mo)_2(C,N)               0
HEXAGONAL         3              2.79             0      4.46           Cr_2C                               0
FCC                           2            10.6454         0      0                Cr_21.34Fe_1.66C_6       0
CUBIC                      1             8.9                0      0                Cr_12Fe_36Mo_10          0
TETRAGONAL       5             9.17              0      4.741         CrFeMn-Sigma               0
TETRAGONAL       5             3.037            0      7.391         CrNbN                              1

The crystal structure data present in 'ppt.dat' was collected from 'Selected Powder Diffraction Data for Metals and Alloys, JCPDS International Center for Diffraction Data, Pennsylvania, USA, 1978'. The user can add or modify the data according to the format.

2) The camera constant may be known. In the present program a typical camera constant is given as an example.

3) The program needs input of length of r from a pair of reciprocal lattice vectors and the angle between the two vectors concerned. The angle between pair of vectors should be given with respect to vector r₀ , as shown in the following figure.

During calculations crystallographically equivalent solutions can be avoided, but this may increase the computing time required.

Example:

FILE name to input to CRYSTAL.FOR : P137_0412

INPUT FILE name of PRECIPITATES DATA : ppt.dat

Camera Length (mm) : 1370

*********************************************

                 FOR JEOL 200 at 200 kV on 2-6-2000
                          Camera Length[cm]      Camera Constant
                             82                      0.02439
                             137                     0.02452
                             205                     0.02527

*********************************************

Camera Constant (A) : 0.02452

Do you wish to avoid crystallographically
equivalent solutions (0 = No, 1 = Yes) : 1

Specify maximum range of Miller Index
Typical value = 3 (avoid values > 4)
Larger values lead to longer run times : 4

Accuracy of measurement ? (Typical value 0.03) : 0.03

No. of Planes to Index: 3

R0 (mm): 12.4

R1 (mm): 16
Angle between R0 and R1 : 45

R2 (mm): 21
Angle between R0 and R2 : 130
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References

H.K.D.H. Bhadeshia, The Geometry of Crystals, Institute of Metals, London, 1987.
H.K.D.H. Bhadeshia, Chapter on crystallography in Microstructural Characterisation of High Temperature Materials, ed. E. Metcalfe, Institute of Metals, London, 1988.

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Parameters

Input parameters

N/A - complete program

Output

All output is to 'filename.out'

Example:

Precipitates data file : ppt.dat

Camera length : 1370.000 mm

Camera Constant : 0.024520 A

Maximum range of Miller Index: 4

Accuracy : 0.030

R[0] = 15.00000 d[0] = 2.28333
R[1] = 16.25000 d[1] = 2.10769 Angle = 24.000 [R0 - R1]

R[2] = 6.60000 d[2] = 5.18939 Angle = 90.000 [R0 - R2]

*********** SELECTED PRECIPITATES **************

TYPE CODE a b c PRECIPITATE

ORTHORHOMBIC 4 4.525 5.087 6.743 Fe_3C
CUBIC 1 10.591 0 0 Fe_23(C,B)_6

           ***********************************************************
           **                                                       **
           Lattice Parameters "a", "b", "c" ?

ORTHORHOMBIC SYSTEM 4.5250 5.0870 6.7430 ANGSTROMS

D1=   2.28333306
D2=   2.107692
Angle between 2.28333306 and   2.107692 =   24.
------------------------------------------------------------------------------
    Vector 1                            Vector 2                                      Zone Axis

(h k l) d (h k l) d [U V W] Angle

0. -1. -3. 2.0559 0. 0. -3. 2.2477 1.0000 0.0000 0.0000 23.8

D1=   2.28333306
D2=   5.189394
Angle between 2.28333306 and   5.189394 =   90.
------------------------------------------------------------------------------
    Vector 1                   Vector 2               Zone Axis

(h k l) d (h k l) d [U V W] Angle

0. -1. 0. 5.0870 0. 0. -3. 2.2477 1.0000 0.0000 0.0000 90.0

D1=   2.107692
D2=   5.189394
Angle between 2.107692 and   5.189394 =   66.
------------------------------------------------------------------------------
    Vector 1                   Vector 2               Zone Axis

(h k l) d (h k l) d [U V W] Angle

0. -1. -3. 2.0559     0. -1. 0. 5.0870    -1.0000 0.0000 0.0000 66.2
           ***********************************************************
           **                                                       **