Molecular Geometry

XYZ Format (Section-Based)

MOLECULE
  Charge        <int>             # default 0
  Multiplicity  <int>             # default 1
  Units         Angstrom | Bohr   # default Angstrom
END

GEOMETRY
  <ELEMENT>  <x>  <y>  <z>     # one line per atom
  ...
END
  • All coordinates default to Angstrom.
  • Charge and Multiplicity default to 0 and 1.
  • The GEOMETRY block must contain at least one atom.
  • Element symbols are case-insensitive.
  • Multiple geometries (for NEB) separated by a blank line in the same GEOMETRY block.

Z-Matrix Format (Route-Card Only)

Z-matrix input is only supported by the legacy route-card parser. It is detected automatically when the geometry block opens with a charge multiplicity line (two integers). Distances in Angstrom, angles in degrees.

#p rhf/6-31g
0 1
N
H  1  R
H  1  R  2  A
H  1  R  2  A  3  120.0

Variables:
R=1.012
A=106.7

Molecule Properties

The Molecule type provides:

MethodDescription
atomic_massAtomic masses
total_massTotal molecular mass
center_of_massCenter of mass
inertia_tensorMoment of inertia tensor
is_linearLinear molecule detection

These are used for thermochemistry (rotational entropy) and IRC mass-weighting.

Coordinate Units

  • Angstrom (default): 1 Å = 0.529177210903 Bohr
  • Bohr: Atomic unit of distance

Set via MOLECULE Units or task: line:

MOLECULE
  Units  Bohr
END