Chemical Crystallography

+ Frequently Asked Questions

+ Crystals Primer

+ Crystals User Guide

+ Crystals Manual

- Cameron Manual

1. Introduction

2. How To Get Started

3. Data Input

4. Outputting Data

5. Editing The Atom List

6. Obeying Files

7. Graphical Output Devices

8. View Direction Control

9. Include And Exclude

10. Drawing Style Control

11. Connectivity Control

12. Control Of Colour

13. Atom Labelling

14. Other Picture Controlling Commands

15. Symmetry Input

16. Crystal Packing Commands

17. Add And Move - Further Symmetry Related Commands

18. Distance And Angle Calculations

19. Information On Data Held Within The Program

20. Group Definitions

21. Miscellaneous Commands

22. How To Stop The Program

23. Menu Definition File

24. Some Useful Ideas

+ Index

Fri Jun 2 2000

Cameron Manual

Chapter 18: Distance And Angle Calculations

18.1: Method of Calculation

CAMERON allows the user to calculate distances , angles and torsion angles.

In order to perform a distance calculation two atoms lists must be generated. The first list is used as a 'starting atom' and the second list is for 'target atoms'. Distances will be calculated between atoms in separate lists BUT NOT within the lists themselves. The list may be generated in two ways:-


generates two lists - both of which can all the N and all the O atoms. In this case N-O, N-N and O-O distances will be found.
TO These subcommands allow to specify different starting and target atoms.

will only calculated N-O distances. Note that the distance arguments may be either atoms or elements as required.
RANGE This sets the minimum and maximum ranges for displayed distances. The syntax is :-

distances are given in angstroms. If only TWO atoms are present in the atom list then the distance will be outputted irrespective of the range. However, as the full calculation will be carried out first there may be a time delay while the calculation proceeds.

18.1: Method of Calculation

The distances output make use of the symmetry operators in order to find distances within the given range. The starting atom coordinates are NOT ALTERED but those of the target atoms are. The symmetry operators (and any suitable translations) are used to move the target atoms around. The output produced is:-

N1_0      O2      2.323
Operator x y z Translations 0 0 1
N1_0      O2_4    1.114
Operator -x y+1/2 -z Translations 0 0 -1

These show the N1 to O2 distances. The first distance relates to an O2 atom which does not currently exist. The operator and translations shown can be used with ADD to generate the atom if required. The second distance is to an atom (O2_4) which does exist. ie. if no pack number is given for the second atom it is not present in the current list.


These commands are used to find angles and torsion angles between atoms that are in the current list. They are entered in sets of three (or four) as required.