Feature Request

Problem / Motivation

Terminal residues only contain one edge (i.e. heavy atom bonded to neighbouring residue) so they require a different treatment from non-terminal residues when computing residue level rotation and UA level translation axes.
Index-dependent selections are not ideal as they will not be universal, i.e. different force fields might have different indexing of atoms in a residue.

Proposed Solution

The axes will be defined based on three points in a terminal residue, such as the one edge atom alongside the next two bonded atoms within the residue or one bonded atom and the centre of geometry of the other atoms in the residue.

Expected Impact

Residue level rotational/ UA level translational entropy values when using the customised axes are expected to be more accurate and the methodology is expected to be more consistent for different types of residues in polymers.