Liren Large Software Subsidy 13/13.iso/p/p260/1.ddi/ROTOPT.HLP

Text File | 1989-11-02 | 5.2 KB | 94 lines

 displacements entered in suboption [F.3] are erased.

DISPLACEMENTS [F.3]

Displacements are in Angstroms, the first to the right (y) and the second
upwards (z) from the center of the screen or paper.  When this suboption is
exercised, suboption [F.2] is turned off.

The scale grid option [P.3] is useful for showing the actual scaled location
of the center of the structure and in estimating displacements.


┘┌█▄▌▐▀αßΓπΣσµτΦΘΩδ∞φε∩≡±≥≤⌠⌡÷≈°∙·√ⁿ²■  ** Help file SERPOR.HLP - Serial port parameters.

If your pen-plotter dot-matrix or laser graphics printer is on a serial port,
it is always necessary to initialize this port with the data-transmission
parameters (baud, parity, stop bits, data bits).  There is no alternative to
entering these values, which are often set by DIP switches on the printer.
Once the values are entered properly, the port will be initialized whenever
ATOMS is started.


** Help file SYMMET.HLP - symmetry options.

[B.3.2.1] SPACE-GROUP OPERATORS FROM SPACE-GROUP FILE.

The best option for crystals is normally automatic reading of the symmetry
information from a special file (SPCGRP.DAT). In this case, it is necessary
to give only the space-group symbol or number.  For a similar input of point-
group symmetry for molecules, use [B.3.2.2].

When entering a symbol, lower case should be converted to upper case, "bar"
axes are denoted by a capital B preceding the axis, and subscripts are
written as normal numbers, e.g. "PB421C".  Except when alternate orientations
for monoclinic space groups are chosen, the short form of the symbol is used:
for example for group number 63 use "CMCM", not "C2/M2/C21/M".

To select an alternate orientation for monoclinic space groups, you must give
the LONG version of the symbol.  For example, the four orientations of space
group number 15 are B112/B, A112/A, C12/C1 and A12/A1.  If you use the short
form, you get the SECOND setting, which is the third of these.
[B.3.2.2] POINT-GROUP OPERATORS FROM SPACE-GROUP FILE.

This is the normal choice for a molecule, provided the symmetry is
crystallographic and atomic coordinates conform to standard orientations.  It
is not applicable if the symmetry is trigonal or hexagonal and cartesian axes
are used; choose [B.3.2.3] in that case. You are shown the list of point
groups; use EITHER the International or Schoenflies symbol, which are
connected with equals signs.

[B.3.2.3] CARTESIAN MATRICES FROM .SYM FILE.

This option assumes that cartesian axes are in use.  It is the only option
applicable to non-crystallographic symmetry, and it can be used if desired in
any other case.  However, it is usually easier to use one of the other
options for crystallographic symmetry, with the possible exception of
trigonal and hexagonal molecules for which the coordinates are given on
cartesian axes.

This option asks for the name of a file with suffix .SYM, containing the
cartesian symmetry matrices. Give the full name of the symmetry file,
including the .SYM suffix.  Some such files, notably those for pentagonal
(C5, D5, C5V, C5H, D5H and D5D) and icosahedral (I and IH) point groups, have
already been provided.  For other point groups, it will be necessary to run
the auxilliary program SYMGRP to generate the file before running ATOMS; see
section XVI.
[B.3.2.4] KEYBOARD ENTRY OF SYMMETRY OPERATORS.

With this option, you enter the symmetry information in the form in which it
is given in the International Tables, and many reports on structures.  This
is sometimes useful for non-standard settings.  After specifying whether a
center is present and the Bravais lattice type, you enter the "Co-ordinates
of equivalent positions" for the general equipoint, as given in the Tables or
other source.  Basically, you just copy the entries, including commas and
semicolons, as many as you like on a line - break lines after operators,
which end with ** Help file PENCHG.HLP - Pen-change modes.

If you have a multiple-pen plotter, you can elect to run in a single-pen mode,
and conversely if you have a single-pen plotter you can draw with multiple
colors, but you will have to change the pens manually. If you choose the
MANUAL pen-change mode (for a single-pen plotter), the plotter returns to the
zero position after drawing all lines of each color, and you are prompted on
the screen to change pens. Typing "return" after the pen change will continue
the plot.  Pen colors for crystal edges and structure axes are set in option
[K.11]; colors for atoms, bonds and polyhedra are set in the input for these
drawing elements.


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** Help file PENMOD.HLP - Pen plotter type and pen-change mode

[M.2.4] PEN PLOTTER TYPE.

If your plotter has only one pen, enter "single"; if it can change pe