imetchecks the B-matrix and removes linear dependent internal coordinates from your list (their status is changed from
#d). If B is only near singular, a warning is issued and the lowest eigenvalue(s) as well as the corresponding eigenvector(s) are displayed. In this case, you should try to find better internal coordinates (although this may not always be possible). After the command
imet, there may be too few (active plus fixed) internal coordinates, but certainly not too many (because linear dependencies have been eliminated). Perhaps you will have to add new ones or--better!--try command iaut or
iredin the preceding menu.
imet should be used always after creating internal
coordinates with iaut or
idef (especially after
iaut, because this command creates usually an overcomplete
set of internal coordinates).
idefunfolds a little submenu where you can define internal coordinates manually. The exact procedure of the definition will be described below in a separate section.
#ideg(which equals the result of
ideg all) for the molecule as a whole.
imet(see above), because iaut may provide an overcomplete set of coordinates. All coordinates which conflict with the molecular symmetry are set to ignore by iaut.
imanallows you to modify the values of internal coordinates. If you specify a list of atoms a only those internal coordinates which refer to only these atoms will be handled. You will get a list of all (active and fixed) internal coordinates and their current values and you will be able to enter a new value for each of them if you like. Default (
) keeps the value shown. Be aware that all distances are given in atomic units ( 1 a.u. = 52.9 pm).
- ic i x
- This option allows you to change the status of a coordinate, e.g. from active to display or every other combination. The syntax is
ic 5 d, if coordinate no. 5 is to be set to display, or
ic k d, if all active coordinates are to be set to display.
- irem i
- This option allows you to delete definitions of internal coordinates from your list. The indices of the internal coordinates always refer to the full list of coordinates including display and ignore coordinates. To make sure you delete the right ones, use
disi. Also the indices will immediately change if you delete coordinates. If you want to delete several coordinates, this is therefore done most easily if you delete them in order of descending indices (because deletion of a coordinate has only an effect on the coordinates with higher indices). After choosing the coordinates to be deleted, a list of all coordinates involved will be displayed and you will be asked to confirm deletion.
The syntax is simply
irem 5to delete internal coordinate no. 5 or
irem dto remove all `display' coordinates.
will bring you back to the geometry main menu.
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