If the geometry is given as Z-matrix, the default is to optimize the variables on which the Z-matrix depends.
In case of `xyz` input, always all 3N coordinates are optimized, even if the `xyz` input depends
on fewer variables. If Cartesian z-matrix input is used, optimization in full space is only enforced if automatic orientation
is requested using the `MASS`, or `CHARGE` options on the `ORIENT` directive.
See *opt_space* in section 46.2.2 for details.

`SPACE=ZMAT|3N`- Specifies the coordinates to be used in the optimization. Z-matrix optimization is only possible if the geometry is given as Z-matrix.
`OPT3N|3N`- (logical). Same as
`SPACE=3N` `ZMAT`- (logical). Same as
`SPACE=ZMAT`

molpro@molpro.net 2018-09-24