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.