Newman projections are stereospecific, graphic representations of the torsion angles around a particular bond. These projections are much easier to interpret than angle data. Cell and atom information is read from the bdf. Orthogonal atom coordinates are calculated. A bonding matrix is evaluated, containing all bonds with distances within predefined limits. For each particular bond a Newman projection is constructed: all connected bonds are projected on a plane perpendicular to the central bond. Distances and angles are output, as well as a survey of fractional and projection coordinates and a list of dihedral angles. The projection is printed and optionally plotted. A select line may be given to select only those atoms, which are used for the Newman projections.

Bonds between atoms are determined from the atomic radii values on the archive bdf. These radii may be changed by entering an atrad line. A minimum of two bonds must be present to be considered for a Newman calculation and/or plot. The user may also give the bonds in advance. The bondin line then contains the name of the central atom, followed by the names of the peripheral atoms.

All bonds are investigated to determine whether they can be assigned as central bonds for a Newman projection. The criterion is that at least one peripheral atoms is bonded to either of the two central atoms. projax lines may be supplied to define the two central atoms. A projection perpendicular to two arbitrary, not necessarily bonded, atoms can be requested in this way.

Atom positions, related to the original atom positions by internal symmetry, may be used in the Newman plots. They must be defined in bondin lines. Note that once one bondin line is used, the other bonds are not derived; all bonds must be defined with bondin lines. If projax lines are used, the same definitions for the internal symmetry must be given.

A Newman diagram is always printed. A command file for the program PLOTX can be written to NWN. Each plot can contain 1 or 4 diagrams. Plot dimensions as well as heights of characters and numbers can be specified either globally in the NEWMAN line or in plotp lines. A title is plotted at the top of the plot, defaulting to the compound identifier, but the user may specify his own title in a ptitle line.

NEWMAN 
projax C1 C2

A Newman projection along the C1-C2 bond is printed. Data are from the bdf.

NEWMAN plot 4
bondin C1 C2 C6 C10 C11
bondin C2 C1 C3 H1 H2
bondin C3 C2 C4
bondin C4 C3 C5
plotp *7 .30
ptitle just a test

Four diagrams in one plot are written to the command file. Only the specified bonds are placed in the bonding matrix. The heights of the characters in the title is 0.30 .