Group contribution data

Some property models require group contribution data. Group contribution data consists of two parts: a definition for each molecule from which groups it exists, and the data that define the groups. Group contribution data, where available, are automatically loaded from the GC files in the data\ipd folder when you add compounds to your property package definition. Group contribution data are stored with the property package definition, so changing the content of GC files has no effect unless you reload your compounds.

To define, for a compound, which sub-groups it exists of, choose Group Contributions from the Configure menu. From the top-most drop down list, select the property model for which you want to edit the data.

Select the desired compound, and click Add Subgroup to add a sub-group to a molecule definition. Click on the count to change how many of these groups are present in a molecule. To remove a sub-group from a molecule, select the sub-group and click Delete Sub-Group. As a check on the correctness of the definition, the total molecular weight vs. the known molecular weight is displayed at the bottom of the list of sub-groups for the selected molecule.

To edit the available groups, click Edit Groups. You can create new groups by clicking New Group. To change the interaction parameters for groups, click on the parameter. Expressions are accepted. To delete an existing group, click Delete.

To edit the available sub-groups, click Edit Sub-Groups on the Group Contributions page. Here, you can add and remove groups, and set the parameters available for each group. To change a parameter value, click on the parameter value itself. Expressions are accepted.