Multi-Section (Multi-Job) Calculations

A single input file can define several jobs that run in sequence using JOB N blocks. A top-level MOLECULE section supplies charge/multiplicity/units defaults shared by all jobs. Each job has its own task: line and sections.

Later jobs can restart from a prior job's checkpoint using a RESTART section:

• Geometry FromJob=N — start from job N's final geometry.
• Orbitals FromJob=N — warm-start the SCF from job N's molecular orbitals.

title: Water - Opt then high-accuracy single point

MOLECULE
  Charge        0
  Multiplicity  1
  Units         Angstrom
END

JOB 1
  task: RHF STO-3G Optimize

  CONTROL
    PrintLevel       Normal
    WriteCheckpoint  True
    CheckpointName   water_opt.oqw
  END

  OPT
    Algorithm   Berny
    MaxIter     300
    Convergence Tight

    Frozen
      Bond   1 2
      Angle  2 1 3
    END
  END

  GEOMETRY
    O   0.000000   0.000000   0.117790
    H   0.000000   0.755450  -0.471160
    H   0.000000  -0.755450  -0.471160
  END
END

JOB 2
  task: RHF 6-31G* SinglePoint

  CONTROL
    PrintLevel       Normal
    ReadCheckpoint   True
    WriteCheckpoint  True
    CheckpointName   water_sp.oqw
  END

  Restart
    Geometry   FromJob=1
    Orbitals   FromJob=1
  END
END

Frozen coordinates

Inside an OPT section, a Frozen block holds the listed internal coordinates fixed at their starting values during the optimization:

OPT
  Frozen
    Bond      1 7
    Angle     2 1 7
    Dihedral  1 2 3 4
  END
END

Atom indices are 1-based. The optimizer measures each coordinate at the input geometry and enforces it as a hard constraint.

Notes

• Each job writes its own checkpoint (see CONTROL).
• A job that omits GEOMETRY must restart geometry from a prior job's checkpoint.
• The checkpoint stores only the latest section's data per file.