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JCPDS card

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Introduction of JCPDS card

From Mark Rivers (ref)

There are several versions of the formats used for JCPDS files. Versions 1, 2 and 3 used a fixed format, where a particular entry had to be in a specific location on a specific line. Versions 2 and 3 were used only by Dan Shim. This routine can read these old files, but no new files should be created in this format, they should be converted to Version 4. Version 4 is a "keyword" driven format. Each line in the file is of the form: KEYWORD: value The order of the lines is not important, except that the first line of the file must be "VERSION: 4". The following keywords are currently supported:

COMMENT:    Any information describing the material, literature
           references, etc.  There can be multiple comment lines
           per file.
K0:         The bulk modulus in GPa.
K0P:        The change in K0 with pressure, for Birch-Murnaghan
           equation of state.  Dimensionless.
DK0DT:      The temperature derivative of K0, GPa/K.
DK0PDT:     The temperature derivative of K0P, 1/K.
SYMMETRY:   One of CUBIC, TETRAGONAL, HEXAGONAL, RHOMBOHEDRAL,
           ORTHORHOMBIC, MONOCLINIC or TRICLINIC
A:          The unit cell dimension A
B:          The unit cell dimension B
C:          The unit cell dimension C
ALPHA:      The unit cell angle ALPHA
BETA:       The unit cell angle BETA
GAMMA:      The unit cell angle GAMMA
VOLUME:     The unit cell volume
ALPHAT:     The thermal expansion coefficient, 1/K
DALPHADT:   The temperature derivative of the thermal expansion
           coefficient, 1/K^2
DIHKL:      For each reflection, the D spacing in Angstrom, the
           relative intensity (0-100), and the H, K, L indices.

This procedure calculates the D spacing of each relfection, using the symmetry and unit cell parameters from the file. It compares the calculated D spacing with the input D spacing for each line. If they disagree by more than 0.1% then a warning message is printed. The following is an example JCPDS file in the Version 4 format:

VERSION:  4
COMMENT: Alumina (JCPDS 0-173, EOS n/a)
K0:          194.000
K0P:           5.000
SYMMETRY: HEXAGONAL
A:            4.758
C:            12.99
VOLUME:        22.0640
ALPHAT:    2.000e-6
DIHKL:        3.4790      75.0   0   1   2
DIHKL:        2.5520      90.0   1   0   4
DIHKL:        2.3790      40.0   1   1   0
DIHKL:        2.0850     100.0   1   1   3
DIHKL:        1.7400      45.0   0   2   4
DIHKL:        1.6010      80.0   1   1   6
DIHKL:        1.4040      30.0   2   1   4
DIHKL:        1.3740      50.0   3   0   0
DIHKL:        1.2390      16.0   1   0  10

Note that B and ALPHA, BETA and GAMMA are not present, since they are not needed for a hexagonal material, and will be simple ignorred if they are present.