Interactive Definition of Internal Coordinates

If you choose idef in the internal coordinate menu, you will get the following information:

ENTER INTERNAL COORDINATE DEFINITION COMMAND
                <x> <type> <indices>
WHERE    <x>       = k    f    d    i
         <type>    = stre invr bend outp tors linc linp
                    comp ring pyrm bipy pris cube octa
THESE COMMANDS WILL BE EXPLAINED IN DETAIL IF YOU ENTER
<x> <type>? FOR SOME CHOICE OF <x> AND <type>, E.G. k stre ?
DEFAULT=GO BACK TO INTERNAL MAIN MENU    DISPLAY=dis

The means the status (see page ) of the internal coordinate entered (k, f, d, i). The syntax is:

k stre 1 2
d tors 3 6 2 7
f bend 3 4 5
i outp 3 4 7 9

Note that in the third example atom 5 is the central atom of the angle!