The Arachne Molecular Modeller is a powerful yet easy-to-use application which allows molecules to be created, manipulated and displayed on Acorn RISC OS computers.


RISC OS Compliant

It runs under the desktop and adheres closely to the guidelines laid down by Acorn to help you to find it easy to learn and use.

Intuitive user interface

The user interface was designed from scratch to be easy to use without confusing the user with unnecessary technical terms.

Simple Molecule Building & Editing Tools

Elements can be chosen from a Periodic Table window and atoms placed with an Add atom tool. The atoms can then be bonded together using a Bond tool. As they are bonded, atoms move to the 'correct' relative positions (bond lengths and bond angles are looked up from tables of chemical data built into Molecular Modeller).

Other tools allow atoms and fragments to be selected, moved and deleted. A clipboard exists, supporting the usual cut, copy and paste operations with molecular fragments.

Comprehensive Choice of Display Styles

A large number of display styles are supported, including: Display options ('perspective', 'backbone', 'highlights', 'dot structure', 'outline atoms', 'shade atoms' and 'shade molecule') can be used to enhance the display. Any display style can be used during editing, for maximum flexibility.

Creates animations

Molecules can be animationed in seconds, and animations can be stored for later access. The animation above was created by Molecular Modeller.

Structure Prediction Routines

Molecular-structure prediction routines are used as atoms as positioned. Background structure prediction routines can be enabled to position atoms in structures in which, for example, there is ring-strain.

Structure Parser

A Molecular Structure Parser is build into Molecular Modeller. This allows you to type in simple structural formulae, as text, to build molecules. For example, typing in CH3CH2OH will produce ethanol.

A fragments library is provided which can be used within the structure parser. For example, phenol can be built by typing in PhOH.

DTP Support

Molecules can be saved in Sprite and (in most display styles) Drawfile formats for use in other programs such as desktop publishers and word processors.

Molecules can also be printed directly from within Molecular Modeller.

CSSR Format Support

Molecules in the standard CSSR format can be loaded by Molecular Modeller. This allows large, existing libraries of molecules to be viewed and manipulated on the Acorn platform.

Molecular Modeller in use

Molecular Modeller in use

A molecule designed with, and displayed by, Molecular Modeller.
The user-configurable tools pane is visible at the top-left, and the periodic table window at the bottom.


The Arachne Molecular Modeller should run on any computer running Acorn's RISC OS 3.1, 3.5, 3.6 or 3.7 with at least 2MB of RAM. The Molecular Modeller itself is RiscPC and StrongARM compatible. (Unfortunately, the copy protection was not StrongARM compatible, but the latest release removes this.) Full use is made of the better display qualities available on the RiscPC and A7000.

A small bug has been fixed in the latest release, which caused a nasty error in rare circumstances.


This ammonia molecule was captured on a RiscPC and reduced to 256 colours using ChangeFSI.

Updates to 3.80

Legal notice

You are only authorised to download and use this software if you already have a fully-registered copy of the Arachne Molecular Modeller. If you are in any doubt, you should contact Arachne Software.

General details

These updates have been compressed using ArcFS 2.

To update your copy of the Molecular Modeller:

  1. make a backup copy (just in case)
  2. copy the !Modeller in the update archive over your existing !Modeller

If all goes well, you will have an updated version of the Molecular Modeller; if not, please feel free to contact us for help.

Small update from version 3.79g

Most users are expected to have version 3.79g. This small (37K) update contains just the files necessary to:

Click here to download this update.

Larger update for users with older versions of Molecular Modeller

If you have a version older then 3.79, you will need this update instead. Unfortunately, for security reasons, the archive has been encoded. To find out the password, please send the details you wrote on your Molecular Modeller registration form to Arachne Software.

Click here to download this 119K, encrypted, archive.

This document is thought to be correct at time of editing (29 Dec 96) but we can make no guarantees concerning the accuracy of the information provided; this is the World Wide Web! Please don't blame us if it all goes horribly wrong.
Thank you for visiting this site, which has been designed and tested with ANT's Fresco Web Browser.
If you have any comments or queries, please do not hesitate to contact the webmaster.

Return to the Arachne Software home page