Jan. 3, 1997
There are some major new features that have been added to PC-GSAS as well as
small bug fixes and minor modifications. Between the last "news" and this one
I have done a number of unannounced upgrades which involved such minor fixes
that I didn't bother announcing them. The major new features and fixes are:
1. The routines REFLTOBIN and REFLTOASCII, which are used to convert reflection
files to and from an ascii format, have been ported to PC-GSAS. These are
mainly used by folks using the single crystal features of GSAS and need to
move reflection files between different computer systems (i.e. VMS to PC).
2. HSTDMP has been modified so that a period (.) has been placed in the CODE
column of the output. This is to make extraction of the profiles by 3rd party
software (EXCEL, etc.) easier.
3. A new graphical routine, VRSTPLOT, has been added to the system. It produces
very spiffy 3D graphics via the VRML (Virtual Reality Modeling Language,
Version 1.0) format. VRSTPLOT can draw ellipsoids for thermal motion or space
filling spheres for individual atoms. It can draw stick representations of
bonds between selected atoms. It can draw polyhedra instead of balls or
ellipsoids for selected atoms. The polyhedra can have any number of faces; the
only criterion is that the faces are the outermost ones. It can even draw the
C60 polyhedron; one has to "fool" it a bit by adding a dummy atom at the
center of the C60. The atoms and polyhedra are colored according to a set of
color values placed in a new version of the ATOMDATA.DAT file. So carbon is
black, oxygen red, nitrogen blue and all the other familiar colors. Colors have
been selected for about 2/3rds of the periodic table. These can be changed in
VRSTPLOT if desired, 120 colors are available. VRSTPLOT will also draw unit
cell edges, magnetic moment vectors (colored black/red for spin reversal) and
a set of planes for a selected hkl. The output of VRSTPLOT is a file (named
expnam.wrl) that is then viewed by a 3rd party VRML viewer. The viewer reads
the file and displays the picture which can be manipulated as if you had a
model of the structure in your hands. All of the 3D visualization is handled by
the viewer as one moves around the structure. There are any number of these, some
as commercial packages, shareware or even as beta "freeware" versions. Browse
the WWW for VRML, that way you'll find all the choices that are out there.
They each have particular strengths & weaknesses; some do not support the full
VRML 1.0 specification and some are faster (and bigger) than others. I
personally use VRWeb and the viewer that comes with Netscape 3.0; the latter is
very fast but requires more memory than VRWeb. However, this kind of graphics
is very computationally intensive, the performance on anything much less than a
100MHz Pentium is likely to be very disappointing. VRSTPLOT can produce a
drawing (lots of balls & sticks, for example) that will even bring a 200MHz
Pentium Pro to its knees, so be careful what you draw.
4.A serious start has been made to port PC-GSAS to the other platforms; thanks
to Brian Toby. He has also created a Linux version which I will support after
it is released.
5. There were many minor fixes (spelling errors, messed up menu items, etc.)
that were fixed; there seems to be an endless number of these to find. As usual
I do appreciate knowing even the most trivial bug or error.
We thank all of you that have pointed out the various bugs, errors, etc. Many
of the above fixes resulted from your input. Please keep 'em coming!