XRAYDIF1 by Todd Warren Snyder
            14727 Polk Street
            Omaha, NE  68137
           email:  mermtws@engvms.unl.edu

What is XRAYDIF1?

XRAYDIF1 is a shareware version of my theoretical, x-ray
powder diffraction, profile simulator.  It is intended
as an inexpensive substitute for data-based, powder
diffraction profile generators, and as a teaching tool.


Benefits

XRAYDIF1 has the capability to simulate a diffraction profile
for any crystalline element or compound.  The output is
available as an interactive graphics display as well as an
extensive peak summary data file (trace.dat).
It has been tested on hundreds of elements and compounds
with superb agreement of peak locations.


Limitations

This shareware version of XRAYDIF1 has only one limitation with
respect to the registered version.  It can simulate only pure
elements or two-element compounds.
i.e, NaCl, FeO3, Cu... but not MnSO4 or BaTiO3
The registered version is capable of any element or compound!
XRAYDIF1 also neglects temperature effects.
 
Use

XRAYDIF1.exe is a DOS program and runs in VGA mode.
The graphic output may be printed by using graphscr or hpgraph or
any other TSR graphics print program from dos.
The graphic output may also be captured to the clipboard during
a windows DOS session by hitting print-screen.
The only output file is a text file called "trace.dat" which
summarizes the results of the current simulation.

The on-screen instructions are self explanatory, but here are two
examples: Simulation of iron pattern and simulation of rutile pattern.


1) Simulation of alpha iron pattern.
STEP A - start program by typing "XRAYDIF1" from the directory where
         it resides. Hit Enter, then WAIT about 5 seconds.
STEP B - Enter the x-ray tube target material used for the generation
         x-rays.  The default, and most common is Cu. Hit enter.
STEP C - Enter the necessary lattice angles.  Since alpha iron is
         cubic all angles are 90 degrees, the default. Hit enter
         three times.
STEP D - Enter the necessary unit cell edge lengths.(lattice parameters)
         Since all lengths are equal just enter the first one, a.
         Type "2.8665" and hit enter.  Hit enter twice more, the b and
         c lengths will default to 2.8865 angstroms.
STEP E - Enter the number of elements. Type "1" and hit enter.
STEP F - Enter the number of atoms per unit cell.  Since alpha Fe is
         body-centered cubic, there are two atoms per unit cell.
         8*(1/8)+1=2. Type "2" and hit enter.
STEP G - Enter the atomic number(s). Type "26" and hit enter.
STEP H - Enter the positions of the atoms.  The body-centereed cubic
         structure has atoms at positions (0,0,0) and (.5,.5,.5).
         Type "0,0,0" and hit enter.
         Type ".5,.5,.5" and hit enter.
STEP I - The graphical output is now on the screen.
         Use the greater-than and less-than keys to scroll through the
         peaks. A "." will appear above each peak in turn and the
         position/intensity/hkl values will also change accordingly at
         the top of the screen.


2) Simulation of rutile (TiO2) pattern.
STEP A - start program by typing "XRAYDIF1" from the directory where
         it resides. Hit Enter. WAIT
STEP B - Enter the x-ray tube target material used for the generation
         x-rays.  Lets use a Cr tube. Type "2" and hit enter.
STEP C - Enter the necessary lattice angles.  Since rutile is
         tetragonal, all angles are 90 degrees, the default. Hit enter
         three times.
STEP D - Enter the necessary unit cell edge lengths.(lattice parameters)
         Enter the first one, a.  Type "4.59" and hit enter.
         Hit enter once since b=a or type "4.59" and hit enter.
         Enter c. Type "2.96"and hit enter.
STEP E - Enter the number of elements. Type "2" and hit enter.
STEP F - Enter the number of atoms per unit cell.  There are six atoms
         per unit cell, 2 Ti and 4 O. Type "6" and hit enter.
  *NOTE THE FLASHING INSTRUCTIONS*
STEP G - Enter the atomic number for element 1.
         The Ti is at a 4+ valence.  
         For the 1st element (Ti), type "18" and hit enter (22-(+4))=18.
STEP H - Enter the number of atoms of element 1.
         Type "2" and hit enter.
STEP I - Enter the positions of the element 1 atoms.
         The Ti atoms are at (0,0,0) and (.5,.5,.5).
         Type "0,0,0" and hit enter.
         Type ".5,.5,.5" and hit enter.
STEP J - Enter the atomic number for element #2.
         The O is at a 2- valence.
         For the 2nd element (O), type "10" and hit enter (8-(-2))=10.
STEP K - Enter the number of atoms of element #2.
         Type "4" and hit enter.
STEP L - Enter the positions of element #2 atoms.
         The O atoms are at (-.3056,-.3056,0),(.8056,.1944,.5),
         (.3056,.3056,0), and (.1944,.8056,.5).
         Enter these values.
STEP M - The graphical output is now on the screen. etc


REGISTERING - PLEASE DO.
        I think $20 is a reasonable amount for a single user.
   I would expect that if XRAYDIF1 was used for teaching or in an
   industrial setting, the institution could benefit $50 worth.
   I would also negotiate the source code.

Te register send your return address, ph# ... along with payment to:
 
            Todd Warren Snyder
            14727 Polk Street
            Omaha, NE  68137

I will send you a 3 1/2 disk without the '2-elements' limitation.
