6.4 Centroids

VEGA ZZ can manage pseudo-atoms which coordinates are calculated in real time from the positions of other atoms as symmetry center. They are called centroids. A centroid can be used to measure distance, angle, torsion, angle between two planes as a normal atom. In molecular dynamics analysis the centroid position is recalculated for each frame.
To define a new centroid, the user must select the Edit -> Add -> Centroid menu item:

Centroid dialog box

Picking the molecule atoms, the user can add a new centroid. The maximum number of pickable atoms is six (6). Clicking the New button,  a new centroid is added and clicking the Reset button, the atom selection restarts from the beginning:

Centroid dialog box     Centroid

Clicking the Keep fixed checkbox, it's possible to fix the centroid coordinates that so aren't updated dynamically when the coordinates of the other atoms are changed (e.g. during the trajectory analysis or the torsion edit).
To close the dialog box, click Close and to remove all centroids, select Edit -> Remove -> Centroids. The centroids can be removed as normal atoms also. An application example can be the distance measure between two rings:

Example