:term:`CFOUR_COORDINATES <CFOUR_COORDINATES (CFOUR)>`
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      Specifies the type of coordinates used in the input file ZMAT. Value INTERNAL (=0) means that the geometry is supplied in the usual Z-matrix format, while CARTESIAN (=1) means that the geometry is given in Cartesian coordinates. A third option is XYZINT (=2) for which a Z-matrix connectivity is defined, but with values of the internal coordinates defined implicitly by supplying Cartesian coordinates. Note that geometry optimizations are currently only possible for INTERNAL and XYZ2INT. **Psi4 Interface:** Keyword set from active molecule, always CARTESIAN. Above restrictions on geometry optimizations no longer apply.

      * **Type**: string
      * **Possible Values**: INTERNAL, CARTESIAN, XYZINT
      * **Default**: INTERNAL

