GEOMETRY Section

The GEOMETRY section contains the atomic coordinates. It is required.

Format

GEOMETRY
  <ELEMENT>  <x>  <y>  <z>
  ...
END

• One line per atom
• Element symbol (case-insensitive: H, h, C, c, etc.)
• Coordinates in Angstrom or Bohr (set by MOLECULE Units or task: line)
• Whitespace-separated

Example

GEOMETRY
  O   0.000000   0.000000   0.117369
  H   0.756950   0.000000  -0.469476
  H  -0.756950   0.000000  -0.469476
END

Multiple Geometries

For NEB calculations, provide two geometries separated by a blank line:

GEOMETRY
  # Start geometry
  O   0.000000   0.000000   0.100000
  H   0.750000   0.000000  -0.450000
  H  -0.750000   0.000000  -0.450000

  # End geometry
  O   0.000000   0.000000   0.100000
  H   0.750000   0.100000  -0.450000
  H  -0.750000  -0.100000  -0.450000
END

The Images N keyword in the OPT section controls the number of interpolating images.

Notes

• The GEOMETRY block must contain at least one atom.
• Coordinates default to Angstrom unless Units Bohr is specified in MOLECULE.
• Z-matrix format is not supported in the section-based input; use the legacy route-card format for Z-matrix input.