Cameron Manual

This command is used to apply a rotation of n degrees about the x-axis which lies horizontally across the screen. The syntax is:

 XROT n
 

These two commands are identical to XROT except for the axis about which the rotation is carried out. The y-axis lies vertically up the screen and the z-axis is perpendicular to the screen.

This command is a 'shorthand' for the previous three commands as it allows you to apply three successive rotations by entering only one command. The syntax is :-

 ROT x y z
 

Note that the order of rotation is: rotate about x then y then z. The order of rotation is important - YROT 10 XROT 5 ZROT 15 will NOT produce the same result as ROT 5 10 15 as the rotation matrices are non-commutative.

This command allows the user to control rotation with the cursor keys. Each time a key is struck a rotation of 5 degrees is applied about the relevant axes. After each key stroke the molecule is rotated and then re-drawn. To speed up this process the molecule is drawn in line style during the CURSOR rotation and is not scaled. The set-up prior to CURSOR is restored once rotation is terminated. The keys used are:

 Rotation about the x-axis
 
 Positive      up arrow
 Negative      down arrow
 
 Rotation about the y-axis
 
 Positive      left arrow
 Negative      right arrow
 
 Rotation about the z-axis
 
 Positive      Delete key (PC)
 Negative      End key (PC)
 

Any other key stroke will terminate the CURSOR control and draw the resultant picture.

In some cases it is useful to be able to define a PLANE and then set the view direction to be perpendicular to it. The syntax of this command is :-

 PLANE at1 at2 at3 ...
 

At least 3 atoms must be used to define the plane (element names will not be accepted). If more than 3 are used then the program calculates the best plane through the atoms and projects onto this.

Alternatively you may want to view onto a particular crystallographic face of the unit cell. The syntax for this command is:

 FACE h k l
 

where h k and l are the Miller indices of the FACE in question.

It is possible to define the view direction as that looking down an interatomic direction. The direction is specified by inputting :-

 ALONG at1 at2
 

As with PLANE atoms not elements must be used as the arguments. Note that the view direction is calculated as that looking down the at1 - at2 direction ie at1 is the closest of the two. The reverse view will be obtained by requesting ALONG at2 at1. ALONG also has a sub-command associated with it:

 ALONG AXIS x
 

These two commands are similar to ALONG except that the at1 - at2 direction is oriented up (VERTICAL) or across (HORIZONTAL) the screen as required.

This command requires three arguments, at1 at2 and at3. It will generate a view direction looking along the bisector of the at1-at2-at3 angle. The syntax is:

 BISECT at1 at2 at3
 

where at2 is the apex atom.

The 'title' command of this group of commands is VIEW. IT IS A VERY IMPORTANT COMMAND. This requires no arguments as causes a picture to be output to the current output device (see SCREEN). The picture is generated according to all of the parameters that are set up prior to its use. For example:

 XROT 10 VIEW
 

will rotate the molecule by 10 degrees about x and then draw a picture.

 VIEW XROT 10
 

would draw the picture first and then carry out the rotation. This rotation would not be observed until the next VIEW is entered.

COPY is the equivalent command for hardcopy output. COPY must be followed by a filename to which the output will be send. HARDCOPY must have been used prior to this to specify the output type. The filename may be one that has already been used in the current run of CAMERON in which case the user is given an option to append the information.