TUM Quantum Chemistry Laboratory
Prof. N. Rösch


To specify the structure of a molecule it is convenient to use internal coordinates, such as bond distances, bond angles, and dihedral angles. A widely used system of internal co-ordinates is the Z-matrix where the six redundant co-ordinates are eliminated by providing no structure information for the first atom (3 redundant parameters), the bond distance only for the second atom (2 redundant parameters), and only bond distance as well as bond angle for the third atom (1 redundant parameters). For all other atoms, one specifies bond distance, bond angle, and dihedral ange. To set up a Z-matrix, the following input parameters have to be specified:

Have a look at the example hydrogen peroxide H2O2.

Atom Distance to atom Angle Dihedral angle
N1 symbol N2 N1-N2 special
N3 N1-N2-N3 special
N4 N1-N2-N3-N4 special
no. no. Å no. degree no. degree
Dihedral angle in HOOH

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Copyright © 2003 N. Rösch, Technische Universität München