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Last modified: Thu Apr 18 11:52:38 2013.
NAME:
JCPDS::COMPUTE_D
PURPOSE:
This procedure computes the D spacings of the material.
It can compute D spacings at different pressures and temperatures.
CATEGORY:
MCA object library
CALLING SEQUENCE:
jcpds->COMPUTE_D, pressure, temperature
OPTIONAL INPUTS:
Pressure: The pressure in GPa. If not present then the pressure is
assumed to be 0.
Temperature: The temperature in K. If not present or zero, then the
temperature is assumed to be 298K, i.e. room temperature.
OUTPUTS:
None. The D spacing information in the JCPDS object is calculated.
PROCEDURE:
This procedure first calls
JCPDS::COMPUTE_VOLUME.
It then assumes that each lattice dimension fractionally changes by
the cube root of the fractional change in the volume.
Using the equations for the each symmetry class it then computes the
change in D spacing of each reflection.
EXAMPLE:
Compute the D spacings of alumina at 100 GPa and 2500 K.
jcpds = obj_new('JCPDS')
jcpds->read_file, 'alumina.jcpds'
jcpds->compute_d, 100, 2500
r = jcpds->get_reflections()
Print out the D spacings at ambient conditions
print, r.d0
Print out the D spacings at high pressure and temperature
print, r.d
MODIFICATION HISTORY:
Written by: Mark Rivers, April 8, 2000.
(See jcpds__define.pro)
NAME:
JCPDS::COMPUTE_V0
PURPOSE:
This procedure computes the unit cell volume of the material at zero
pressure and temperature from the unit cell parameters.
CATEGORY:
MCA object library
CALLING SEQUENCE:
jcpds->COMPUTE_V0
OUTPUTS:
None. The V0 information in the JCPDS object is calculated.
PROCEDURE:
This procedure computes the unit cell volume from the unit cell
parameters.
EXAMPLE:
Compute the zero pressure and temperature unit cell volume of alumina
jcpds = obj_new('JCPDS')
jcpds->read_file, 'alumina.jcpds'
jcpds->compute_V0
MODIFICATION HISTORY:
Written by: Mark Rivers, May 22, 2000
(See jcpds__define.pro)
NAME:
JCPDS::COMPUTE_VOLUME
PURPOSE:
This procedure computes the unit cell volume of the material.
It can compute volumes at different pressures and temperatures.
CATEGORY:
MCA object library
CALLING SEQUENCE:
jcpds->COMPUTE_VOLUME, pressure, temperature
OPTIONAL INPUTS:
Pressure: The pressure in GPa. If not present then the pressure is
assumed to be 0.
Temperature: The temperature in K. If not present or zero, then the
temperature is assumed to be 298K, i.e. room temperature.
OUTPUTS:
None. The volume information in the JCPDS object is calculated.
PROCEDURE:
This procedure computes the unit cell volume. It starts with the
volume read from the JCPDS file or computed from the zero-pressure,
room temperature lattice constants. It does the following:
1) Corrects K0 for temperature if DK0DT is non-zero.
2) Computes volume at zero-pressure and the specified temperature
if ALPHAT is non-zero.
3) Computes the volume at the specified pressure if K0 is non-zero.
The routine uses the IDL function FX_ROOT to solve the third
order Birch-Murnaghan equation of state.
EXAMPLE:
Compute the unit cell volume of alumina at 100 GPa and 2500 K.
jcpds = obj_new('JCPDS')
jcpds->read_file, 'alumina.jcpds'
jcpds->compute_volume, 100, 2500
MODIFICATION HISTORY:
Written by: Mark Rivers, April 8, 2000. Original work by Tom
Duffy. Ideas from Dan Shim.
31-May-2000 MLR Issue warning if K0 is 0, but return 0 pressure volume
06-Sep-2000 MLR Change to Anderson thermal pressure EOS for high P+T
27-Feb-2001 MLR Add support for dk0pdt and dalphadt.
13-Mar-2001 MLR Put addtional sanity check (f ge 0.) in BM solver.
17-Mar-2001 MLR Replaced home-grown solver for BM equation of state
with IDL FX_ROOT function. It is much faster,
more accurate, and more robust.
(See jcpds__define.pro)
NAME:
JCPDS::GET_REFLECTIONS
PURPOSE:
This function returns the information for each reflection for the
material. This information is an array of structures of type
{JCPDS_REFLECTION}.
CATEGORY:
MCA object library
CALLING SEQUENCE:
r = jcpds->GET_REFLECTIONS()
OUTPUTS:
This function returns an array of structures of type
{JCPDS_REFLECTION}. The current definition of this structure is:
{JCPDS_REFLECTION, $
d0: 0., $ ; The lattice spacing at 0 pressure and 298K
d: 0., $ ; The lattice spacing computed by JCPDS::COMPUTE_D,
; at pressure and temperature.
inten: 0., $ ; The relative intensity of this reflection
h: 0, $ ; The lattice index H
k: 0, $ ; The lattice index K
l: 0 $ ; The lattice index L
}
Note that the definition of this structure may change in the future,
but these fields are guaranteed to always exist.
If there are no reflections present in this JCPDS object (for example,
if JCPDS::READ_FILE has not yet been called) then this function returns
-1.
PROCEDURE:
This function simply returns the array of JCPDS_REFLECTION structures
from the JCPDS object.
EXAMPLE:
Compute the D spacings of alumina at 100 GPa and 2500 K.
jcpds = obj_new('JCPDS')
jcpds->read_file, 'alumina.jcpds'
jcpds->compute_d, 100, 2500
r = jcpds->get_reflections()
Print out the D spacings at ambient conditions
print, r.d0
Print out the D spacings at high pressure and temperature
print, r.d
MODIFICATION HISTORY:
Written by: Mark Rivers, April 8, 2000.
(See jcpds__define.pro)
NAME:
JCPDS::READ_FILE
PURPOSE:
This procedure reads a JCPDS file into the JCPDS object.
CATEGORY:
MCA object library
CALLING SEQUENCE:
jcpds->READ_FILE, file
INPUTS:
File: The name of the file to read.
OUTPUTS:
None. The file is read into the JCPDS object itself.
PROCEDURE:
This procedure read the JCPDS file. 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.
EXAMPLE:
jcpds = obj_new('JCPDS')
jcpds->read_file, 'alumina.jcpds'
print, jcpds->get_reflections()
MODIFICATION HISTORY:
Written by: Mark Rivers, April 8, 2000.
16-May-2000 MLR Increased maximum number of lines from 100 to 1000
27-Feb-2001 MLR Added DK0PDT and DALPHADT.
(See jcpds__define.pro)
NAME:
JCPDS::WRITE_FILE
PURPOSE:
This procedure writes a JCPDS file from the JCPDS object.
CATEGORY:
MCA object library
CALLING SEQUENCE:
jcpds->WRITE_FILE, file
INPUTS:
File: The name of the file to written.
OUTPUTS:
None. The file is written from the information in the JCPDS object.
PROCEDURE:
This procedure writes a JCPDS file. It always writes files in the
current, keyword-driven format (Version 4). See the documentation for
JCPDS::READ_FILE for information on
the file format.
EXAMPLE:
This reads an old format file, writes a new format file.
jcpds = obj_new('JCPDS')
jcpds->read_file, 'alumina_old.jcpds'
jcpds->write_file, 'alumina_new.jcpds'
MODIFICATION HISTORY:
Written by: Mark Rivers, April 8, 2000.
(See jcpds__define.pro)
NAME:
JCPDS_BM3_INVERSE
PURPOSE:
This function returns the value of the third order Birch-Murnaghan
equation minus pressure. It is used to solve for V0/V for a given
P, K0 and K0'.
CATEGORY:
MCA object library
CALLING SEQUENCE:
result = JCPDS_BM3_INVERSE(V0_v, Pressure)
INPUTS:
V0_v: The ratio of the zero pressure volume to the high pressure
volume
OUTPUTS:
This function returns the value of the third order Birch-Murnaghan
equation minus pressure.
COMMON BLOCKS:
The common block BM3_COMMON contains MOD_PRESSURE, K0 and K0P. The
use of a common block is required to pass this information, because
FX_ROOT does not call the user function with any additional parameters.
PROCEDURE:
This procedure simply computes the pressure using V0/V, K0 and K0',
and then subtracts the input pressure.
EXAMPLE:
Compute the difference of the calculated pressure and 100 GPa for
V0/V=1.3 for alumina
jcpds = obj_new('JCPDS')
jcpds->read_file, 'alumina.jcpds'
common bm3_common mod_pressure, k0, k0p
mod_pressure=100
k0 = 100
k0p = 4.
diff = jcpds_bm3_inverse(1.3)
MODIFICATION HISTORY:
Written by: Mark Rivers, March 17, 2001.
(See jcpds__define.pro)
NAME:
JCPDS__DEFINE
PURPOSE:
This function defines an object of type JCPDS. It cannot be called
directly, but is invoked when an object of type JCPDS is created by
IDL.
CATEGORY:
MCA object library
CALLING SEQUENCE:
jcpds = obj_new('JCPDS')
OUTPUTS:
OBJ_NEW creates and returns an object of type JCPDS.
SIDE EFFECTS:
This procedure defines structures of type JCPDS and JCPDS_REFLECTION.
EXAMPLE:
; Create a JCPDS object and read a file into it.
jcpds = obj_new('JCPDS')
jcpds->read_file, 'alumina.jcpds'
MODIFICATION HISTORY:
Written by: Mark Rivers, April 8, 2000.
May 22, 2000 MLR Added JCPDS::COMPUTE_V0 method
(See jcpds__define.pro)