[gmx-users] Assigning Improper Dihedrals to an Index Group

[Mark Abraham]

Darrell Koskinen wrote:
> Hi Justin,
> I want to assign the improper dihedral "improper_Z_CA_X_Y" to all 
> dihedrals within an index group. I would prefer not to write code to 
> insert "1" into the "function type" field followed by the improper 
> dihedral reference. Is there a command I can issue that will insert the 
> correct function type code and improper dihedral reference into my .top 
> file for the dihedrals associated with a specific index group?

No, index groups aren't able to be used here. I don't think there's any 
solution other than editing the .top file. If you might need to do this 
more than once, than using something like

#define normal_improper whatever_it_should_be
#define modified_improper improper_Z_CA_X_Y

and then using these #defines for the relevant functions might be 
useful, because now you can just change the definition once.

Mark