User`s guide

2. Building Molecules

Z-Matrix Editor Dialog Box

Two steps are required to change the z-matrix for the current molecule: first reorder the

atoms as desired, and second adjust the connectivity definitions. These steps must be done in

this order.

To reorder the atoms, change the numbering in the Order column (negative and decimals are

OK) and click the ReOrder button. The atoms will be resorted in numerical order. Note that the

connectivity definition will likely change during this process.

To adjust the connectivity definitions, change the atom numbers in column Na (Length), Nb

(Angle), and Nc (Dihedral) as desired, and click the ReConnect button. Note that atoms can only

reference atoms above them in the z-matrix.

The Z-Matrix Editor is used to specify which coordinates should be optimized or fixed during

the calculation. To optimize or fix a coordinate, set the corresponding Opt entry to O (optimize)

or F (fix), respectively. The Opt All and Fix All buttons optimize and fix all of the coordinates,

respectively.

The Z-Matrix Editor is also used to specify that a coordinate should be scanned in the calculation.

To scan a coordinate, set the corresponding Opt entry to S (Scan). Then enter the desired Start,

Stop, and # Steps values. Note that # Steps represents the number of points in addition to the

first point.

If an atom is added or deleted, a new default z-matrix is created, and previous z-matrix edits are

discarded.